WASHINGTON (AP) _ It was in November 1947, before the dawn of the jet era of commercial aviation, that David L. Behncke, president of the Air Line Pilots Association, demanded tough action to counter the threat of aircraft fires, including complete fireproofing of cabin interiors.

Behncke testified at a congressional hearing shortly after 52 people were killed when a United Airlines DC-6 caught fire during a flight and crashed against a hillside in Bryce Canyon, Utah, on Oct. 24, 1947. The fire was blamed on fuel from an overflowing tank that was ignited by a cabin heater.

The chief spokesman for U.S. airline pilots accused the aviation industry of putting ''speed, payload and productivity'' ahead of passenger safety, and asked: ''Which is more important - the dollar or human lives?''

Nearly 38 years later, many of Behncke's recommendations have been observed for a long time but some others, including cabin fireproofing and replacing wing fuel tanks with self-sealing fuel cells, are still being debated.

Progress toward protecting passengers against aircraft fires has been slow and frustratingly difficult.

''Whereas other aspects of commercial aviation have developed and improved by leaps and bounds, cabin safety standards have basically remained unchanged since the late 1950s,'' said John O'Brien, ALPA's director of engineering and air safety, in congressional testimony a year ago.

Since O'Brien made that observation, the Federal Aviation Administration has intensified its efforts in two major areas of fire safety:

-Reducing the lethal effects of aircraft fires, notably from smoke and toxic fumes from burning cabin materials.

-Testing a chemical jet fuel additive that is intended to prevent leaking fuel after a crash from bursting into a fireball that is virtually impossible to survive.

The FAA's efforts were spurred by a fire that erupted aboard an Air Canada DC-9 during a June 1983 flight and forced the plane to make an emergency landing at Cincinnati. The 23 victims all died of smoke inhalation and carbon monoxide poisoning, a coroner said.

Ironically, the fuel additive was designed to prevent the sort of rapidly escalating blaze that engulfed a British Airtours charter jet, killing 54 people, after its left engine exploded during takeoff from Manchester, England, on Aug. 22.

The FAA said Wednesday it plans to order mandatory airline inspections of the Pratt & Whitney model JT-8D engine, the type that exploded aboard the British Boeing 737 and which powers about two-thirds of the nearly 3,000 jet planes in U.S. commercial service.

Federal experts say 40 percent of the people who die in plane crashes after surviving the initial impact are killed by fire. But FAA spokesman Fred Farrar says, ''There's not much that can be done to prevent the fires.''

Last October, the FAA ordered airlines within three years to outfit cabin seats and cushions with fire-retardant covers that are supposed to delay by as much as 40 seconds the point at which they burst into flames, igniting a fireball.

The agency also ordered installation within two years of special floor lights intended to guide passengers to emergency exit in a smoke-filled cabin.

Last March, the FAA ordered installation of smoke detectors in aircraft lavatories within 18 months. In addition, the airlines were given two years to install automatic fire extinguishers in lavatory trash receptacles and hand- held extinguishers in other strategic cabin locations.

The agency is close to issuing a final rule requiring more flame-resistant materials for baggage compartment liners, and is seeking to establish new flammability standards for cabin interiors.

The government's difficulties in solving the problem of fire safety were dramatized last December when a test of the fuel additive went awry during a highly publicized, $11.8 million demonstration crash of a remote-controlled Boeing 720 in the Mojave Desert at Edwards Air Force Base, Calif.

The test plane was enveloped in a fireball explosion, despite use of the additive that is supposed to turn extremely volatile fuel vapors into a non- flammable gel upon impact.

The government blamed the fireball on the plane hitting the ground at the wrong angle, but said the additive nevertheless ''performed perfectly.'' The FAA rejected the airline industry's claim that the test was a failure.

Rep. Norman Mineta, D-Calif., chairman of the House Public Works and Transportation subcommittee on aviation, said in a telephone interview that the FAA is ''finally making progress now'' on fire safety measures after what he called ''a foot-dragging approach for many years.''

But Mineta vowed that his panel would watch closely to make sure the Reagan administration, in the face of aviation industry complaints, does not back down from enforcing deadlines for complying with the new fire safety rules.

''When it comes to saving a life, yesterday isn't fast enough,'' Mineta said.