Is the nation's commercial air fleet adequately prepared to fight hazardous fire and smoke? The recent in-flight fire aboard an Air Canada DC-9 leading to 23 deaths from smoke inhalation, and more recently an engine fire and a washroom wastebasket fire on two airliners during the weekend lend new urgency to the question.
Its answer is decidedly mixed.
Several forward steps have been taken during the last decade.
For instance, the Federal Aviation Administration (FAA) has banned all smoking in airplane washrooms. Smoke detectors are required in many cargo compartments. And, within the last year or so, the airlines have voluntarily replaced traditional carbon-dioxide fire extinguishers in 80 percent of their fleet with Halon extinguishers, which emit halogenated hydrocarbons and are more effective in putting out fires.
In addition, extensive research aimed at finding ways to decrease fire and smoke hazards has been conducted by the FAA itself and a variety of other government and industry sources.
But most aviation-safety experts outside the FAA and many who watch over this area in Congress argue that the time between testing and adopting such measures - if the measures are adopted at all - is much too long. Rep. Elliott H. Levitas (D) of Georgia, who chairs a House subcommittee that will hold hearings on aviation fire and smoke issues in July, insists that government safety standards are seriously outdated.
''The FAA tends to keep looking for the perfect answer before they do what they can do,'' agrees Charles Miller, an independent air safety consultant.
For its part, the FAA argues that it must take into consideration other factors, such as need and cost. It must weigh every aspect of any change it may make, the FAA says.
For the last decade or so, the National Transportation Safety Board (NTSB) has urged the FAA to follow the lead of the military by adding polymers to airplane fuel to make fuel tanks more resistant to post-crash fires. Without the additive, the refined kerosene changes from a liquid to a highly combustible mist in the event of a rupture to the tank.
FAA spokesman Fred Farrar says the change would be a major leap forward in fire protection, but the agency must first study the additive's effect on aircraft engines.
Similarly, the FAA is not about to rush into requiring airlines to cover their highly flammable polyurethane seat cushions with a rubberlike material that can delay ignition by as much as 50 seconds - despite NTSB urging, more than a decade of materials testing, and a ready admission by the FAA that the idea works.
Mr. Farrar says the durability of the materials, their weight, and their cost still are being studied.
Ultimately, the FAA makes its own decisions. Neither the breadth of support nor the duration of the push for a safety idea necessarily makes a critical difference.
''We've had a lot of (fire) recommendations outstanding for a very long period of time,'' says NTSB spokesman Brad Dunbar.
For years, the NTSB, Air Line Pilots Association (ALPA), Association of Flight Attendants, and, more recently, the Special Aviation Fire and Explosion Reduction Committee (SAFER) have prodded the FAA to require some means - such as smoke detectors and automatic fire extinguishers - by which fire or smoke in plane lavatories could be detected immediately. Tests show that because of the heavy flow of forced air in lavatories, a good three minutes can elapse before any smoke can be seen coming out the door.
Technically, the safety proposal is still open on FAA books. In general, smoke detectors ''tend to be valuable in cargo compartments where there isn't any other way to detect smoke, but in-flight there are always people around,'' Farrar says.
''What about washrooms? ''They're used all the time by passengers. Doors are opened and shut.''
Another improvement that several organizations are pressing for sounds relatively simple and inexpensive: Place emergency exit lights at arm-rest level or lower, so that passengers trying to escape by keeping close to the floor can still see the exits through the smoke.
Technically this proposal, too, remains open. But Farrar says, ''We have to look at whether or not it's really going to make any difference.''
The FAA spokesman argues that in-flight fires generally are not as serious a problem as post-crash fires. He says of the 50 in-flight fires during the last five years, half involved engines and the others were easily put out by hand-held fire extinguishers.
Aviation-safety experts in and out of the FAA admit the search for more effective ways to fight fire and smoke, particularly in materials, is very complex. Treating a material with a fire retardant, for instance, may delay the moment of ignition but also could produce more toxic gas and smoke than otherwise. Similarly, many say it currently is impossible to come up with a fireproof material. If hot enough, even metal will burn.
John Enders, who first worked on such projects with the National Aeronautics and Space Administration after the Apollo fire in 1967 and later served as chairman of SAFER (established by the FAA in the late 1970s), says, ''The options really aren't all that many.''
''The real key to all this is early detection of fire and smoke,'' insists Mr. Enders, who now is president of the Flight Safety Foundation. ''The sooner you intervene, the easier it is to control or extinguish (a fire).''
''I think it's a mistake to concentrate too much on cabin materials,'' agrees Vic Hewes, a retired pilot for Delta Airlines who chaired ALPA's aircraft rescue and fire committee for more than 30 years. ''The fact is, we're going to have little fires here and there from time to time - if we know about them in time, we can catch them.''