LOS ANGELES, FEB. 8 -- Trembling in shock and smoking a cigarette, Robin Lee Wascher sat in a Los Angeles airport control tower office after guiding two airliners onto the same runway and seeing them collide in a ball of flame.

"I'm sorry. I'm sorry," the 38-year-old controller murmured over and over, tears spilling fitfully from her brown eyes.

Outside, firefighters were pumping flame-smothering foam into the smoldering wreck of a USAir Boeing 737 and pulling out victims. The crash last week killed 34 people -- all 12 people on a SkyWest Metroliner and 22 of the 89 aboard the larger USAir jet.

But in the minutes immediately following the accident, all Wascher knew was that there had been a collision and a fiery explosion. The eight-year veteran controller was so anguished over the safety of the passengers that no one could tell her that a third of them had died.

This picture of grief and remorse was painted by another controller, one of many of the small, brown-haired woman's colleagues who spent hours after the accident counseling her and hid her in hotels to protect her from publicity.

"To say that she's remorseful is probably redundant," said the colleague, who spoke on condition of anonymity. "How would you feel if your worst nightmare had come true? An accident like that is our worst nightmare. . . . We all think about it. It's what we're trained not to do."

Off-duty controllers escorted Wascher home after the accident and spent the night comforting her. The next day, as news spread that controller error was a factor in the disaster, friends took her to a hotel near the airport. Fellow controllers stayed with her, and she met with a private counselor provided by the Federal Aviation Administration.

"If it had happened to me, I don't know that I could have handled it as well," said Wascher's colleague. "She is a very strong person."

Being interviewed for three hours Wednesday by National Transportation Safety Board officials was especially tough for Wascher, the colleague said.

In that interview, Wascher said she had confused the SkyWest plane with a similar commuter plane that was behind a larger plane on a taxiway. Because another controller misplaced some paperwork, she said, she was unaware that the plane she saw on the taxiway was a Wings West craft -- and not the SkyWest plane.

As a result, she said, she cleared the USAir jet to land. It rear-ended the smaller craft, flattening it and dragging it in flames into the side of an abandoned fire station.

"This incident, this accident, could have happened to anybody, any of us," said Wascher's colleague.

Wascher, who is on administrative leave, has begun to consider what she will do after public hearings on the accident are held in three months. "She's made indications that she wants to come back," one colleague said.