Fire Extinguishers, Smoke Detectors, and the FAA
The FAA has an expansive regulatory mandate—to certify the air-worthiness of new aircraft, to control the nationwide air traffic control system, to regulate pilot certification, and to police airline operations and maintenance. The agency functions by leaving much to the discretionary judgment of the airlines and airframe manufacturers. Aviation technology is so complicated that the FAA realized years ago it did not have the resources or expertise to pass judgment independently on all new airframe designs. Instead, "designated engineering representatives," engineers employed by the airframe manufacturers, certify new airplanes for the agency. Matters of operation and maintenance are almost as complicated as aircraft design, involving highly technical systems and countless potential subjects for regulation. Airframe manufacturers employ hundreds of safety engineers and continually issue bulletins and warnings to their customers, the airlines. Airlines adopt their own safety routines and maintenance procedures as well. Confronted with the complexities of aviation safety, the FAA proceeds with a mixture of deference, prodding, and formal regulation. All three strategies are reflected in the evolution of the FAA's regulation of fire extinguishers and smoke detectors on commercial airlines.
Prodding takes the form of advisory circulars and general notices, both of which are "non-binding" but carry significant weight with the airlines. Smaller airlines with limited engineering capacity to develop their own standards are likely to adopt these recommendations. Larger carriers do their own evaluation, cognizant of the cost of ignoring government recommendations should something go wrong. Formal regulation usually follows from the most serious accidents and those that result in National Transportation Safety Board (NTSB) recommendations that have been made before. How these stages take shape depends on the seriousness of the accident and the nature of any prior experiences.
In the case of fire extinguishers and smoke detectors, the formal) standard was largely influenced by two tragic accidents: the Varig fire in 1973 and the Air Canada fire a decade later. Before these tragedies, however, the FAA long took a deferential approach toward fire extinguishers, mandating simply that "the type and quantity of extinguishing
agent must be suitable for the kinds of fires likely to occur in the compartment where the extinguisher is intended to be used." The airlines and airframe manufacturers were left to determine what was "suitable." The agency provided additional guidance with the advisory circular in 1965 that recommended up to three fire extinguishers per airplane and sanctioned the use of carbon dioxide extinguishers.  It contained no actual product specifications such as capacity, discharge time, or nozzle type. Nor did it speak to the placement of extinguishers or the training of personnel in their use.
Cabin fire safety attracted intense attention in 1973 when a terrible in-flight fire killed 124 people on a Varig Airlines Boeing 707 en route to Paris from Rio de Janiero. The fire, attributed to a discarded cigarette in a lavatory wastepaper disposal unit, broke out shortly before landing. Thick black smoke soon filled the cabin and cockpit. The pilots literally stuck their heads out the window in order to make a forced landing a few miles from the airport. Of the 135 people on board, only eleven survived; the remainder died of asphyxiation or from toxic gas. The NTSB focused on facilitating earlier detection and more effective suppression through smoke alarms and smoke masks for flight attendants respectively. The NTSB made numerous recommendations, including requirements for "a means of early detection of lavatory fires … such as smoke detectors or operating procedures for the frequent inspection of lavatories by cabin attendants." The FAA opted for more "No Smoking" signs, an appeal to the airlines for better monitoring by the crew, and a promise that the "FAA has begun a preregulatory study of the feasibility and justification for a requirement for smoke detectors in lavatories."
The advisory circular on fire extinguishers was completely out of date by the late 1970s, failing to take into account changes in airplane size and extinguishant technology. New jumbo jets with a seating capacity in excess of three hundred require many more extinguishers than the old planes. Virtually all airlines carried more extinguishers than suggested in the circular. Some also used the new Halon extinguishant, a liquid gas that extinguishes fire by chemically interrupting the combustion chain reaction (rather than by physically smothering it). Halon is a derivative of halgonated hydrocarbon. It is suitable for use in cold weather, leaves behind no chemical residue to contaminate or corrode aircraft parts, and can be three times more effective than carbon dioxide extinguishers of equal weight.
Boeing provided it on all new airplanes after 1979, but Halon still
was not mentioned in the FAA advisory circular until a series of "volatile liquid hijackings" raised concerns about the capability of current extinguishers. (The hijackers in these cases carried jars of gasoline, threatening to set the plane on fire.) The FAA's Office of Civil Aviation Security sponsored a study of hand-held fire extinguishers by the Factory Mutual Research Corporation. The FAA quickly revised the advisory circular on fire extinguishers to explain the advantages of Halon. The circular did not require Halon, however, and it provided no additional product specifications. The agency stepped up the pressure after tests at the FAA Technical Center revealed that Halon was better than carbon dioxide or dry chemicals at extinguishing volatile liquid fires. The agency's strategy, something between unsolicited advice and formal regulation, was to issue a general notice. G-NOTs, as they are known in the agency, are formal requests for "voluntary" compliance with a suggestion. They are the FAA's way of putting the airlines on the spot—requesting a specific safety improvement and requiring a formal response concerning the airlines' intentions. The agency accordingly issued a general notice on November 29, 1980, requesting all airlines to carry at least two Halon extinguishers.
About half of the carriers indicated that they had complied or would do so. A few expressed mild resentment at the FAA's refusal to take responsibility for the issue. If Halon was desirable, argued the vice president for engineering and quality control at Frontier Airlines, "there are regulatory means of requiring it rather than encouraging such devices be installed without providing sufficient justification." Several carriers worried about the possible toxic effects of Halon extinguishers. Some of this concern was prompted by warning labels. ("Use in an enclosed place may be fatal," warns the label on a Kidde hand-held Halon extinguisher.) But the evidence about the toxic effects of Halon in aviation use was limited and mixed. Boeing conducted live fire tests and endorsed the use of Halon, although the engineers refused to release their test data. American Airlines also conducted tests, and declined to use Halon because it left behind "a strong bromine smell that caused burning eyes and coughing."
The FAA relied on mild coercion until June 2, 1983, when an in-flight fire killed twenty-three people on an Air Canada flight near Cincinnati. The FAA was backed into a regulatory stance toward fire extinguishers and smoke detectors. As a rulemaking staff member put it, the agency gets "one free bite" in adopting regulatory strategies; that is, it has the most discretion in deciding how to address issues being raised
for the first time. But the FAA had already had one bite at these issues, The agency had tried gentle and coercive "advice" on fire extinguishers, and the NTSB had already recommended smoke detectors. New regulations would certainly follow. Their genesis is so clearly in the Air Canada disaster, however, that it is necessary to recount some details of that tragedy.
The Air Canada Fire
Stories from the survivors of the fire, which eventually killed twenty-three people, were sensational, frightening, and widely publicized. A fire broke out in the lavatory of the DC-9, and, as in the Varig fire, thick acrid smoke soon filled the plane. During its emergency descent to the Greater Cincinnati Airport, described by one passenger as "like an elevator ride," the pilot's chair was literally on fire. His vision was totally obscured by the time he landed the plane, tires exploding on impact. Flames burned through the roof of the fuselage, and scenes of firefighters combating the blaze with foam and water topped the national news.
The complete story, pieced together from separate reports by the National Transportation Safety Board and a special investigative unit of NFPA, is much less dramatic than the emergency landing and rescue effort. It all began with an electrical short in a lavatory pump. Three circuit breakers tripped in the cockpit, and a crew member tried without success to reset them. Eleven minutes later, a flight attendant detected smoke emanating from the lavatory. An attendant entered the lavatory, saw smoke coming from the wall liner, and discharged a carbon dioxide fire extinguisher in the general vicinity. Minutes later a second extinguisher was also discharged, and the smoke appeared to clear; but a flight attendant checking on the situation soon thereafter found the lavatory door so hot it was considered unsafe to open. The smoke reappeared and got worse. A master caution light in the cockpit signaled an electrical system failure. The pilot decided to make an emergency landing. It took ten minutes to land the plane. Visibility approached zero as the plane filled with smoke. Only those passengers who reached the emergency exits within about one minute of landing got out of the plane safely. The rest apparently succumbed to carbon monoxide poisoning.
Aviation accidents are almost never attributed to a single cause. Usually a combination of mechanical and human factors are involved.
With fires, the direct "cause" of any particular incident is obviously the ignition source. In that sense, a short circuit in the lavatory flushing pump caused the Air Canada fire. The consequences of ignition, however, depend on the combustibility of surrounding materials, the quality of fire detection and suppression, and various elements of the emergency response. Accordingly, the extensive damage from the Air Canada fire—the consequences of ignition—can be attributed to the delay before the crew detected and responded to the fire, the ineffective use of the fire extinguishers, the toxicity of the seat covers, and the difficulties encountered in evacuation.
Accident investigators tend to take an expansive approach when determining the "cause" of an accident. Aware that regulations are influenced by accident reports, investigators often seek to effect the greatest possible change. "It's better if you don't find the exact cause because then only one thing will get fixed," according to an NTSB investigator. Instead, for every serious accident the NTSB recommends a laundry list of changes in FAA regulations.
The Air Canada incident was no exception. Many culprits were identified. The NTSB was particularly critical of the crew for the delay between detecting the fire and deciding to land. A few independent experts consider this criticism unfair but concur that the crew was ineffective in its use of fire extinguishers. The NFPA report emphasized the problems of smoke and toxic gas, suggesting the need for more research on flammable materials, particularly seat covers. The NTSB wanted several things "fixed" as a result of the fire. It immediately recommended that the FAA inspect lavatory flushing pumps and establish a procedure for verifying whether the circuitry had been damaged over time. Three months later it recommended, among other things, the installation of smoke detectors and the use of Halon fire extinguishers.
Political Pressure and a Prompt Proposal
Every fatal airplane accident generates extensive media attention and strong political pressures. Congressional committees have an almost limitless inclination to investigate airplane accidents. In his study of policy analysis in the FAA, Steven Rhoads notes that "it would be difficult to overestimate the seriousness with which Congress views commercial air crashes." Within two months of the accident, three separate congressional committees held hearings on the Air Canada
fire. Accused of "footdragging" and indifference bordering on callousness, the FAA soon became Congress's scapegoat for the incident. Congressman Dan Burton (R-Ind.) made the exaggerated claim that "had [Halon extinguishers] been on-board Air Canada nobody would have died." Several congressmen introduced bills to mandate the NTSB's proposals on smoke detectors and Halon fire extinguishers. Congress was unlikely to regulate the matter by statute, however, since it had neither the inclination nor the resources to address such technical questions. (In any case, as one congressman put it, "I would not want to fly in a plane designed by Congressional committee.") Instead Congress strengthened the oversight process. One committee required the FAA to file monthly progress reports on the implementation of various NTSB recommendations. The pressure to adopt new regulations, including ones concerning fire extinguishers and smoke detectors, was intense.
The FAA knew it had to respond to the Air Canada fire with a regulation and was prepared to do so quickly. In short order the agency drew on its previous experience and drafted a simple standard. First, smoke detectors would be required in airplane lavatories and galleys. No effort was made to define the technical specifications for these devices. Second, a built-in fire extinguisher would be required in the towel disposal receptacle of each lavatory. (This had been suggested by the NTSB after both the Varig and Air Canada fires.) Finally, the number of fire extinguishers required would be increased, and at least two Halon 1211 extinguishers would be required on every plane. The choice of Halon 1211, and the exclusion of Halon 1301, was apparently based on the general notice sent out after the gasoline hijackings. The increase in the number of extinguishers required was simply an incremental guess. "We took a look at the wide bodies," a rulemaking staff member stated, "and said 'we need another extinguisher for every one hundred people.'" Otherwise, to a large extent, the NTSB essentially drafted the regulation.
Objections to the proposal were meek. The American Transport Association, which represents most major airlines and is considered by many to be a powerful lobbying organization, did not oppose "the basic thrust" of the proposal, only the requirement for smoke detectors in galley areas. The few other objections to the rule were technical. Some engineers argued that the standard should permit Halon 1301 as well as Halon 1211 (the numbers denote differences in chemical structure). Others alleged that household smoke detectors would not necessarily be reliable in airplanes. The effects of vibration were cited by Underwriters
Laboratories as one of several possibly significant aspects of aviation use that might impede performance. Unusual air currents might also be important, particularly in airplane lavatories, where the air moves down and out through the toilet bowl.
These claims might have been self-serving—UL was basically advocating that the FAA require laboratory certification of smoke detectors for aviation use—but they were also well founded. Devices designed specifically to endure the rigors of the aviation environment are far more sophisticated than a standard household detector. Detectors for airplane cargo holds, produced in accordance with an FAA Technical Standards Order, cost $800 to $1,300 each. When the Regulatory Analysis Division in the FAA first analyzed the proposed rule, they used cost estimates based on these devices and arrived at a benefit-cost ratio of less than one. The critical but unanswered question is to what extent accuracy and reliability are sacrificed by allowing the basic dime store model instead of the sophisticated aviation model. Household detectors are not particularly sturdy either. Given the rigors of aviation use, they might not work in time of need. (Liability concerns of this nature prompted at least one major manufacturer to decline an airline's recent order for 1,500 detectors.) Missing batteries, a problem noted by carriers that experimented with smoke detectors, could also incapacitate the smoke detector. Petty theft would not be the only motive. Sabotage by smokers breaking what is widely thought to be one of the most ignored FAA prohibitions—against smoking in the lavatory—is another possibility.
Another possible consequence, argued an official of the British Civil Aviation Authority, is false alarms, which would "soon give rise to a loss of faith in the detection system." Household detectors are sensitive to changes in air flows, something that occurs regularly in flight but seldom at home. Smoke is also common in galley areas, partly as a by-product of food preparation. Several airlines feared that the panic caused by an activated alarm might be worse than the possibility of a fire going undetected without a smoke detector.
Technical Objections and a Final Rule
The other technical objections to the proposed FAA standard concerned either the fire extinguishant or the nozzle configuration. Several manufacturers argued that Halon 1301 should be permitted in addition to
Halon 1211. Halon 1211 discharges in a more liquid state than Halon 1301 and has better range and direction in use. But Halon 1301 is considerably less toxic than 1211, so it may be advantageous in small areas such as the cockpit. The use of Halon 1301 in hand-held fire extinguishers is relatively recent. There were no hand-held Halon 1301 extinguishers when the FAA issued its general notice in 1980. Three years later, Metalcraft, Inc., received Factory Mutual Research Corporation's first approval for such a product. UL still did not list any. So there was limited information about the merits of this technical question.
The FAA balked and refused to consider the Halon 1301 alternative because, according to an FAA rulemaking staff member, "1301 is not rated for a Class A fire." The reference is to the UL method for rating fire extinguishers by type of fire and extinguisher capacity. But the reasoning is flawed because UL's Class A fire is simply too big. "Halon is effective on an 'A' fire," notes a fire protection engineer, "but the smallest 'A' fire [that UL builds] takes about nine pounds of agent." Hand-held extinguishers usually have three to five pounds. There may be technical reasons for restricting the use of Halon 1301, particularly in large cabin spaces, where it might be less effective than Halon 1211, but the reason offered by the FAA indicates no understanding of these issues.
A few commenters suggested that the FAA require flexible discharge hoses on all fire extinguishers. This would be particularly helpful in battling fires in concealed spaces, overhead, or under the seats. Fixed nozzles, which are supposed to be operated in an upright position, are difficult to operate under such circumstances. Tests conducted by one airline suggested that flexible nozzles increased effectiveness by an incredible magnitude of ten. The FAA showed little interest in this issue. The rule was published in final form less than four months after the comment period closed. There was only one significant change: smoke detectors would not be required in the galley. This eliminated the airlines' strongest objection without compromising on anything the staff considered critical. The safety record with galley fires was far more reassuring than the record for lavatories. There has never been a catastrophic in-flight fire, domestic or foreign, that originated in the galley. While this requirement was easily dropped, addressing the other objections raised in the comment period was not so easy. They called for changes in specific requirements and would require additional analysis. The FAA had no patience for these arguments. The agency wanted to placate Congress and get the rule published. The rulemaking staff had
no intention of letting public comments delay the process. The candid explanation of a staff member about comments concerning the value of requiring a flexible hose on Halon extinguishers illustrates the attitude: "There probably is a lot of benefit in a flexible hose. But we have a certain practical limitation here: we can't just go ahead in the middle of a rule action and change our minds and say that when the rule comes out we want twenty-five hundred airplanes to be equipped with flexible hoses. That throws everything into a cocked hat…. We had to make a decision and we made it." The rule was finalized in record time. It was promulgated on March 29, 1985, less than ten months after it was first proposed. Three years later, the FAA banned smoking on all domestic flights of under two hours. This may be the most cost-effective move the FAA could take toward reducing the risk of a cabin fire. The ban was adopted for health reasons, however, not for reasons of fire safety.
Evaluating the FAA Standard
Whether the FAA's new regulation would have prevented the Air Canada disaster or, more important, another catastrophe in the future is difficult to determine, partly because serious accidents are so rare. There were no deaths on U.S. commercial aircraft in 1980, for example, and only four in both 1981 and 1984. Even 1985, considered by many "the worst year ever" for aviation safety, was remarkably safe by comparison to other modes of transportation (particularly if deaths due to terrorist acts are subtracted from the total). Accidents are so rare, according to an actuary Metropolitan Life, that "it is almost pure chance as to which [major commercial airline] has a total loss" in any given year. The chances of a serious in-flight fire are even more remote. Most aviation injuries and fatalities are caused by impact, not fire. As an airline safety engineer put it, the fatal in-flight fire is "a rare animal of a rare breed." The first recorded fatalities from an in-flight cabin fire in the United States were in the Air Canada calamity.
The almost random nature of accidents creates the first paradox of developing (or analyzing) aviation safety regulations. Accidents precipitate strong political pressures for regulatory change, but they provide little factual basis for making meaningful improvements. Preventing random events is practically an impossible task. Instead of trying to anticipate the unknown, attention tends to get focused on preventing any repetition of what has already happened, regardless of the likelihood that it will happen again.
The politics of aviation safety also conflict with broader political trends concerning government regulation. Many members of Congress openly challenge the notion that aviation safety regulations should be undertaken only if benefits are at least commensurate with costs. Testifying before a House committee about several recent proposals for upgrading cabin safety, the chairman of the NTSB said he "would hate to see [their] implementation delayed for a cost-benefit analysis." Nevertheless, the FAA is bound by the same executive orders that require all agencies to conduct an economic analysis of proposed regulations.
This raises the second dilemma of aviation regulation: the FAA must justify in economic terms regulations that sometimes can only be justified on other grounds. This is not to say that the FAA's Regulatory Analysis Group engages in trickery or deception. The agency has refined the use of economic analysis over the years through its capital improvement projects for airport facilities. A detailed FAA manual spells out the procedures and many specific values (including the always controversial value of a life) to use in cost-benefit analysis. This simplifies and standardizes the agency's analysis. Nevertheless, this case demonstrates how the use of favorable assumptions can make a regulation of questionable economic benefit look economically desirable.
The FAA's Regulatory Analysis Group wrote a forty-three-page cost-benefit analysis of the proposal for smoke detectors and fire extinguishers. The analysis is systematic, comprehensive, and prominently featured in the Federal Register notice. The bottom line, according to the analysis, is that "total expected benefits equal $42.8 million and total costs equal $13.8 million, resulting in total expected benefit-cost ratio of 3.1 and a total expected net benefit of $29.0 million." There is much to take issue with in this analysis. For example, smoke detectors, assumed to cost $50 each, will very likely cost much more if airlines choose even a few of the features justified by the aviation environment (for example, tamper-proof battery packs, better vibration tolerance).
More important, there are several reasons to call into question not only the magnitude of estimated benefits but whether they actually exceed expected costs. One problem concerns predicting catastrophic in-flight fires. Recognizing the difficulty in predicting the distribution of essentially random numbers, the FAA staff utilized an elegant statistical solution: the Poisson distribution. The elegance of the solution masks the significance of one critical underlying assumption: the "expected mean value" of two catastrophic cabin fires in the next ten years. This
figure is purportedly based on "historical data." The Varig fire occurred in July 1973 and the Air Canada fire in June 1983. But the Varig fire was neither on a domestic carrier nor a domestic accident. The Air Canada fire caused the first fatalities in the United States from an in-flight cabin fire. To expect two similar fires every ten years seems overly gloomy, especially since there have been improvements in aviation fire safety since the Varig incident. After that fire, several airlines installed heat-sensitive fire extinguishers in trash receptacles. Moreover, there is nothing magic about a ten-year period. Thomas Hopkins, an economist at the University of Maryland's School of Public Affairs, notes in connection with the FAA's analysis of Floor Proximity Emergency Lighting—another proposal linked to the Air Canada fire—that "if the past five years are considered more representative of what lies ahead, there were no pertinent fatalities and so no plausible benefits." One problem with the agency's cost-benefit analysis, then, is that it does not test the sensitivity of this important assumption. Assuming a mean of one catastrophic fire (instead of two) every ten years could cut the potential benefits of the rule in half.
Other assumptions of vital importance to the analysis include the estimated "coefficients of effectiveness" for smoke detectors and fire extinguishers. Here the analysis purports to incorporate "conservative" estimates. These estimates are not as unambiguously "conservative" as the FAA staff suggests. One assumption is that a smoke detector could avert 50 percent of catastrophic lavatory fires. The staff provides no basis for this estimate or for labeling it "conservative." Stated another way, the coefficient is based on two assumptions: first, that in 50 percent of the lavatory fires that become catastrophic, quicker detection would prevent the catastrophe; and second, that off-the-shelf smoke detectors would actually provide quicker detection. Both assumptions are doubtful. Speed of detection certainly was not the problem in the Air Canada fire. The short-circuit alarm probably alerted the pilots faster than a smoke alarm would have. Delays and uncertainty in responding to the alarm—something as likely to occur with smoke detectors as with circuit breakers—were the main problems. Second, the detection capability of household smoke detectors in an aviation environment, as already mentioned, is quite uncertain. False alarms are likely to be a problem; some fires may go undetected. Combining these considerations, it appears that 25 percent, or maybe even 10 percent, is as reasonable an estimate as 50 percent. Similar arguments apply to the coefficients used for calculating the benefits of trash receptacle extinguishers.
A third problem with the economic analysis is that it overstates the benefits by failing to take into account existing "compliance" with the proposed rule. At least half of the commercial carriers voluntarily complied with the FAA's 1980 request to carry Halon extinguishers (a few even installed smoke detectors without any FAA advice). The benefits attributable to the proposed rule should reflect only the incremental benefit of adding Halon extinguishers to the remaining carriers. Instead, the FAA adjusted the cost figure to reflect the marginal cost of Halon extinguishers but not the marginal benefits.
The cost-benefit analysis also did not take into account the special training necessary to use a Halon extinguisher effectively. This means either overstated benefits or understated costs, depending on whether the airlines voluntarily improve existing training programs. Most airline employees receive cursory instruction in fire fighting. Only two airlines provide actual "hands on" training with fire extinguishers. "Hands on" training is particularly important with Halon extinguishers, which discharge in a liquid stream that must be carefully applied because it lasts less than ten seconds. Those not properly trained in the use of these sophisticated extinguishers may actually be less effective than with other extinguishers. Even with less-sophisticated extinguishers, untrained operators are generally able to extinguish only about half as big a fire as those with training. The carbon dioxide extinguishers aboard the Air Canada jet were discharged without effect in the early stage of that disaster. As an engineer with Factory Mutual Research Corporation put it, "It wouldn't have made any difference if you had given them another thirty extinguishers." The cost-benefit analysis never considered this issue. In fact, the provision for Halon extinguishers was given only superficial treatment. The staff considered these extinguishers "clearly cost-beneficial" because they are lighter than older extinguishers, so "fuel savings alone are expected to pay for this proposal." In short, they were assumed to be more effective. The projected $2.9 million in "pure safety benefit" might be more than outweighed, however, by the cost of training flight attendants adequately to ensure effective use.
Finally, even if the FAA were predisposed to write its own standard, the rulemaking staff should have been aware that the private standard NFPA 408 existed. At least one FAA employee has been on the NFPA's Aircraft Rescue and Firefighting Committee, charged with standards for aviation fire extinguishers, since NFPA 408 was first adopted in 1956. Two FAA representatives were on the committee when the standard
was revised in 1980 and later when the FAA decided to draft and adopt its own standard. One reason the rulemaking staff was unaware of NFPA 408 is organizational. Neither of the FAA employees were from the Airworthiness Division—the division that wrote the FAA's standard for fire extinguishers—and neither took a particular interest in NFPA 408. They were more interested in other aircraft rescue and firefighting standards. Beyond these peculiar circumstances, however, the fact that the rulemaking staff did not think to check for the existence of an NFPA standard is evidence of the low profile that currently characterizes these standards.
None of these issues was raised by those commenting on the proposed rule or, surprisingly, by the Office of Management and Budget in its review of the cost-benefit analysis. Politics, it seems, loomed larger than economics. "This was a motherhood issue," explains an FAA rulemaking staff member. "Who is going to argue about fire extinguishers in airplanes?" Indeed, the FAA received hundreds of handwritten letters and postcards from individual citizens in favor of the proposed rule.