WASHINGTON (AP) _ Flight attendants couldn't open all the exit doors and threw passengers seat cushions for use as life preservers in the frantic evacuation of USAir Flight 5050, a flight attendants' union spokeswoman says.

''The floor of the plane buckled up and down like a roller coaster,'' said Cindy Yeast of the Association of Flight Attendants, which gathered information Thursday about the crash from its members assigned to the USAir jetliner.

The flight attendants and cockpit crew were not made available to news media after the Wednesday night crash at New York's LaGuardia Airport. Federal investigators indicated they also were having difficulty late Thursday finding crew members in their effort to determine why the plane skidded off the end of the runway.

The condition of the airliner, which broke into three pieces, made it impossible for flight attendants to get all the exit doors open, Ms. Yeast said. Two people sitting in the back of the nine-month-old plane were killed.

''When the flight attendants realized passengers were going into the water, they ripped off seat bottom cushions and began throwing them out the door,'' she said.

Current rules call for life vests only on flights that go more than 50 miles over major bodies of water.

Congress passed a law in 1987 requiring the Federal Aviation Administration to make rules that would put life vests for all passengers on all flights by U.S. carriers. The FAA has proposed but not implemented the rules.

Flight attendants and pilots began petitioning the FAA for universal installation of life vests in 1980.

Ms. Yeast said door slides can be used as rafts in cases where planes go into the water, and most seat cushions also are designed to float. Some passengers said they stayed afloat after the USAir crash by clinging to driftwood in the water.

After most passengers evacuated, flight attendants and the plane's captain tried to use the inflated escape slide as a raft to reach several passengers caught in the rear of the cabin, Ms. Yeast said. But the slide deflated, apparently punctured by debris, she said.

The interior of the plane was dark, filling with water and shifting in the current, Ms. Yeast said, as passengers yelled for help from behind a place where the floor had buckled to the cabin ceiling. Rescue crews helped pull out several passengers.

Ms. Yeast said the pilot and last flight attendants stayed in the aircraft trying to free passengers and left only after rescue workers arrived and ordered them to evacuate.

People were in the water for as long as 30 minutes, she said, and some started singing as they awaited rescue.

Ms. Yeast identified the flight attendants on the flight as Wayne Reed, Jolynn Galmish, Susan Harrelson and Kelly Donovan, all based in Baltimore. The airline declined to release the names of the cockpit crew.