Sixty-seven people aboard USAir Flight 1493 survived the fiery collision with a smaller plane Feb. 1 in Los Angeles. They scrambled out exits as choking smoke and heat spread through the cabin. But 17 others who managed to unstrap their seat belts and move toward exits died within a few feet of safety.

The crash again has raised questions about how far the government should go in requiring airlines to build fire safety into passenger cabins.

Numerous steps have been taken in the last decade to give passengers a few seconds or minutes extra to escape crashes after they have survived the impact. But still unresolved are what further steps, some of them costly, should be required. Should cabin sprinkler systems be installed? Should passengers be given smoke hoods? Should seats near window exits be removed?

The USAir jetliner was an older plane that had some of the new fire-retarding technology, but not all of it.

The seats were made of a material designed to slow the spread of flames. The plane contained fire extinguishers, smoke hoods for the cabin crew, floor-track lighting to guide passengers to exits and other fire safety measures required by the Federal Aviation Administration in the last few years.

But it did not have carpeting and wall and ceiling fabrics designed to reduce flammability and heat release. The FAA now requires such materials on new airliners and requires that they be installed on older planes when they go through a major maintenance check. The USAir plane had not been through such a check since the rule became final last Aug. 20.

The crash provides almost a textbook illustration of the effectiveness of current fire safety systems. The impact was almost fully survivable for passengers on the Boeing 737.

Although all passengers and crew were killed in the smaller SkyWest plane, and the captain was killed on the USAir flight, one passenger on the 737 was found buckled in his seat, apparently the only person unable to attempt an escape. Other dead passengers were found near window exits or apparently trying to reach door exits.

By all accounts, flight attendants did their job professionally. One attendant died and another was injured at the front of the plane, possibly because they stayed behind to help passengers. The two attendants at the rear apparently saved lives by quickly opening escape doors and authoritatively directing passengers through the darkness and heat toward the doors.

Although one exit jammed and another was blocked by fire, four others opened and many passengers managed to escape. The airport fire department arrived within one minute, investigators said, and began pouring foam into the open window exits immediately. Several passengers said they felt their way to safety by going toward the cool spray from the foam.

With so many things going right, why were 17 people unable to get out?

Whether reduced-flammability materials would have provided the extra moments that would have allowed them to escape is something the National Transportation Safety Board (NTSB) will not determine for weeks or months.

The board also will try to determine the source of the fire. The 737's fuel tanks remained largely intact, meaning the only major source of burning fuel had to come from the SkyWest Fairchild Metroliner buried under the 737.

NTSB member Jim Burnett said Friday that the board is sending a fire-damaged oxygen bottle from the 737 cargo compartment to the FBI Fire Science Lab in an effort to determine the nature of the damage and why there was any fire in that area.

It is clear, according to federal investigators, that current systems did help passengers survive. Burnett said several passengers reported that the floor-track lighting, which the FAA required to be installed, helped them escape.

Just as the crash probably will produce new fire safety recommendations, many of the current rules were spurred by previous crashes. For example, a lavatory fire on an Air Canada DC-9 on July 9, 1982, which killed 23 before the plane could make an emergency landing at Cincinnati, led to the FAA's rules on fire-resistant cabin materials.

Critics charge that the FAA is going too slow, particularly on long-standing efforts to make window exits more accessible -- either by removing a seat next to the exit or making the space between the rows wider at window exits. Matthew H. Finucane, director of air safety and health for the Association of Flight Attendants, said it is "unforgivable" that the FAA has taken more than five years to act on the issue.

Finucane said the British Civil Aviation Authority moved quickly to provide greater access to window exits after a British Airtours Boeing 737 suffered an engine fire and aborted its takeoff from Manchester International Airport in 1985. Although the plane stopped on the runway and firefighters arrived 30 seconds later, 55 people died in the ensuing fire, partly because of difficulty getting out exits. Yet, the FAA still has not acted, he said.

"Many people are still dying in survivable crashes," Finucane said.

Anthony J. Broderick, the FAA's associate administrator for regulation and certification, said he can understand why some critics grow impatient with the regulatory process. But he said it is also the FAA's job to be sure the proper action is taken and no harm is done. He said removing one seat from exit doors would chop 2 percent of an airplane's revenue generating capacity. "Spreading the seats is a more reasonable approach, one that we are analyzing," he said.

Broderick said the FAA has promulgated dozens of fire safety rules over the last few years that have helped passengers survive, including requiring fire-resistant materials, automatic fire extinguishers in lavatories and cargo compartments, lavatory smoke detectors and floor lighting. "What I think you see is the fruits of a regulatory process that is really aggressive," Broderick said.

Fire safety advocates, such as the Aviation Consumer Action Project, say providing passengers with smoke hoods could increase their chances of surviving. Other groups want airplanes equipped with sprinkler systems.

There is widespread resistance to smoke hoods in the industry and government, partly because many experts feel passengers would delay their exits to put on the smoke hood, defeating its purpose.

Walter S. Coleman, vice president for operations at the Air Transport Association, said research has shown that people resist putting something over their heads when they are already choking, even if they know it will help them breathe.

However, a major worldwide effort is underway to produce a cabin sprinkler system that would spray a fine mist of water from the ceiling, dissipating hot gases and slowing the point of "flashover," when the gases erupt into an unsurvivable fire.

Jim Likes, director of payload systems at Boeing, said such a system seems simple to install, and some tests show promise. But numerous complicated safety questions remain to be answered, he said, such as the impact on the high-voltage systems in modern aircraft if the sprinkler system inadvertently starts during flight.