LAS VEGAS (AP) _ A half-naked, underage girl had to be removed from a hallway of leering aviators at the Tailhook convention the same weekend former Navy Lt. Paula Coughlin said she was sexually harassed, a hotel security officer testified.

Jim Vernon, a security officer at the Las Vegas Hilton for 20 years, said Wednesday he ''saw pants flying in the air'' and found an intoxicated girl on the floor without her pants on during the September 1991 convention.

He and another guard took the girl out of the hallway before investigating what had happened because, as he asked Coughlin's lawyer Dennis Schoville, ''If you were a female with your pants off would you want to be around 500 men?''

Vernon said none of the aviators could tell him what happened to the girl, whose mother was called to get her. Vernon warned a Tailhook official against allowing similar incidents, but nothing else was done, he said.

Vernon testified in Coughlin's federal lawsuit against the Hilton and the Hilton Hotel Corp. She was the first to publicly accuse Navy and Marine aviators of sexual assault, saying she was forced to walk a lecherous gantlet. Coughlin claims the Hilton was negligent in not controlling the aviators and could have prevented the attack.

Earlier, Adm. Donald Boecker testified Coughlin was a ''superb'' officer who never seemed the same after the convention.

''I noticed a change in her demeanor,'' Boecker said. ''She was scared. She was frightened. She had been violated.''

Boecker, in a videotaped deposition, said Coughlin was his aide for eight months during 1990 and 1991 at the Naval Air Testing Center in Maryland.

He described her as a ''great aviator'' who flew a half dozen different types of helicopters and was a top candidate for advancement. She was no longer his aide during the convention, but Boecker said he saw her a few weeks afterward.

After Coughlin spoke out, about 90 women followed with similar complaints, and a dozen filed lawsuits. Her revelations ignited a scandal that led to the resignation of Navy Secretary H. Lawrence Garrett III and the early retirement of Chief of Naval Operations Frank B. Kelson III.

The Navy and Marine Corps pursued 140 harassment cases, but none led to a court-martial.

Coughlin wanted to stay in the Navy, but eventually quit because she felt harassed by other Navy officers for taking the scandal public, Boecker said.

Coughlin's is the first case to go to trial. She settled last week with the Tailhook Association. She is seeking unspecified damages against the hotel.