The Federal Aviation Administration, reacting to the crash of Pacific Southwest Airlines Flight 1771, which investigators believe was brought down by a former employe with a handgun, ordered airlines yesterday to put all employes through the same metal detectors and baggage X-ray equipment as passengers.

The new rule, which takes effect Monday, requires the screening of all employes -- including uniformed flight crews -- working for all U.S. and foreign airlines operating at U.S. airports. Generally, crews and other employes now walk around checkpoints when in uniform and displaying an ID badge.

The action was announced as congressional investigators told a House hearing of widespread security problems at six major airports.

"The types of deficiencies identified were such that, if left uncorrected, they could allow unauthorized persons access to air operations areas and aircraft," said Kenneth Mead, an investigator for the General Accounting Office.

The GAO investigators told a House Government Operations subcommittee that inspectors without identification easily gained access to restricted areas while wearing clothing similar to flight attendants' uniforms and roamed through restricted areas at will.

Flight 1771 piled into a hilly pasture in the coastal mountains northwest of San Luis Obispo, Calif., on Dec. 7, less than two minutes after the pilots reported gunfire on board. All 38 passengers and five crew members died. Investigators believe the crash was caused by David A. Burke, a recently fired USAir employe who smuggled the gun on board to kill the man who had dismissed him, and who then opened fire in the cockpit. Burke was allowed to bypass security checkpoints at Los Angeles International Airport by airline security agents who knew him as an employe, but were unaware that he had been fired Nov. 19. Pacific Southwest is a USAir subsidiary.

The FAA also announced plans to issue rules aimed at requiring airlines and airports to use computers to better track employe identification badges. In its inspection, the GAO found that more than 6,000 employe badges at the Los Angeles airport -- nearly one-sixth -- could not be accounted for.

The new security-check rule was given a cool endorsement by lobbying organizations for the airlines and the Flight Attendants Association. The Air Line Pilots Association (ALPA), which represents 40,000 commercial airline pilots, criticized the move as "an overreaction" to the PSA crash.

"It's very definitely a case of overkill," said Roger Hall, a United Airlines pilot and an ALPA vice president. "The program they're trying to implement far exceeds what is required to deal with the threat. You don't want to get into something that is so horribly overexaggerated that it creates additional problems."

Hall said the rules will further clog the air travel system.

"Do you realize how many employes you're talking about and the number of times they have to go through the security? I'd be hard-pressed to give you a number at an airport like {Chicago's} O'Hare, but flight crews go in and out of there several times a day," Hall said. "You keep multiplying that. It's a huge number of people."

Hall said the ALPA has suggested instead that the FAA issue computerized cards, such as bank cards with individual coded numbers, to allow employes access through locked doors to secure areas.

William Jackman, a spokesman for the Air Transport Association, said the lobbying group tried to get Monday's deadline extended.

"I don't think the airlines have begun to think about the problems this is going to create," Jackman said. The ATA called the present system "a good one that detects thousands of firearms each year."