WASHINGTON - The tape of Betty Ong's voice yesterday, alive and urgent yet amazingly calm, describing through the background buzz how a group of hijackers had stabbed two of her fellow flight attendants and taken over the first plane that slammed into the World Trade Center, silenced the congressional hearing room.

"The cockpit is not answering the phone. ... Someone's coming. ... Another one [passenger] got stabbed. ... Our First Class gal's stabbed, our purser has been stabbed. ... We can't get inside the cockpit," Ong told an American reservations specialist in a call from the rear phone aboard doomed American Airlines Flight 11.

There had been two days of official testimony from more than two dozen government administrators, aviation security experts and law enforcement personnel to the commission investigating the Sept. 11, 2001, attacks.

For the first time, panel members had nothing to say.

Ong's voice, captured on tape, broke only when the aircraft would suddenly plunge at the hands of inexperienced pilots who had taken over the cockpit.

The tape of her call offered some of the first insight and an all-too-real account of what was happening aboard the four hijacked airplanes that morning. It lasted until her plane flew with explosive force into a Trade Center tower.

While her conversation was the most dramatic new revelation at the hearing, commission investigators also released a nine-page report yesterday that said the hijackers probably sprayed Mace around the cockpit area on all four flights, apparently to keep passengers away, and that they convinced passengers to sit quietly on at least one of the flights by announcing over the intercom that there was a bomb on board.

Investigators believe the hijackers might have also used the autopilot and the Global Positioning System to target the World Trade Center and the Pentagon. The report said the flight data recorder found buried in the rubble of the Pentagon indicated the pilot "had input autopilot instructions for a route to Reagan National Airport."

On Ong's flight, the hijackers appeared to have killed at least one passenger - and possibly two - before taking over the aircraft.

The tape recording picks up mid-sentence after an unidentified - and somewhat impatient - reservations specialist had answered the phone.

"The cockpit's not answering the phone," Ong tells the man. "Somebody's been stabbed in Business Class, and, um, I think there's Mace and we can't breathe and I don't know, I think we're getting hijacked."

The man replies, "What seat are you in?" apparently unaware that Ong is a flight attendant.

"Ma'am, are you there?"

"Yes," Ong says, who was having trouble hearing the man.

"What seat are you in?" the man asks, and then again forcefully, "Ma'am, what seat are you in?"

We're bound "for Boston, we're up in the air. The cockpit is not answering the phone," Ong says urgently.

The man replies, "What seat are you in?"

After a pause, Ong says, "I'm in my jump seat right now."

At that point the man seems to realize she is a flight attendant but still does not address what Ong has told him. He pauses and then asks, "What is your name?"