Hundreds of employees with access to high-security areas of airports have been arrested on charges such as using phony Social Security numbers, lying about past criminal convictions or being in the United States illegally, government records show.

Federal law enforcement officials said they have arrested or indicted more than 450 workers at 15 airports in the investigation known as Operation Tarmac.

Many of those arrested are illegal immigrants who could be deported, while others face prison terms of up to 10 years or fines of up to $250,000, say officials of the departments of Justice and Transportation.

``We will not stop until we are satisfied we have a work force that the traveling public can trust,'' Transportation Secretary Norman Y. Mineta said.

The workers arrested had security badges allowing them to get onto planes, ramps, runways and cargo areas, law enforcement officials said. They were employed by private companies, such as those which clean airplanes or operate airport restaurants.

While law enforcement officials said none of those arrested has terrorist links, some aviation experts said the workers were in positions to help smuggle bombs or weapons aboard aircraft, if they wished to do so.

Nearly 140 of the arrests involved workers at Dulles International Airport and Reagan National Airport in the Washington, D.C., area.

Other arrests have come in Baltimore, Phoenix, San Diego, San Francisco, San Jose, Calif., Charlotte, N.C., Boston, Sacramento, Calif., Atlanta, Las Vegas, Seattle, Portland, Ore., and Salt Lake City.

Before Sept. 11, government officials did not give much attention to the threat that an airport employee could hide a bomb on a plane while cleaning the aircraft or restocking the galley, or help someone else to do it, said Mary Schiavo, a former inspector general at the Transportation Department.

Efforts since the 1988 bombing of Pan Am Flight 103 and the 1996 crash of TWA Flight 800 focused on trying to prevent terrorists from putting bombs in suitcases, said Schiavo, now a lawyer representing victims of airplane accidents.

Even after Argenbright Security was fined $1 million in 2000 for failing to sufficiently check its employees' backgrounds, the issue was not a high priority of law enforcement, said Todd Zinser, a deputy inspector general for the department.

``Airport security wasn't at the forefront,'' Zinser said. ``Of course, Sept. 11 changed that. It was much easier for us to develop these coalitions to look at these problems. At the same time, you had the Justice Department more interested in pursuing these cases because of the national emergency.''

An official of one union that represents some immigrants and airport workers believes the effort will not improve security.

``These are people who are working hard, who are paying their taxes and who want to contribute to America,'' said Eliseo Medina, executive vice president of the Service Employees International Union. ``They're not a security threat by any stretch of the imagination.''

Several Justice Department agencies are involved in the investigation, along with the Transportation Department inspector general and new Transportation Security Administration.

But Zinser said that ``what bothers us is that law enforcement has to go out and find these. There aren't other checks in the system that are being used to make sure these gaps don't exist.''

FAA Administrator Jane Garvey in October ordered background checks of an estimated 750,000 airport and airline employees who could enter secured areas of airports. The checks are supposed to be completed by December.

``We're just trying to make sure the rules are followed,'' Zinser said. ``They exist to make sure security is as good as it can be. If you don't enforce the rules, then you have these potential threats.''