WITH ALARMING ease and frequency, Transportation Department investigators penetrated security at a number of major U.S. airports during months of testing in the past year. They breezed through checkpoints, gates and jet bridges all the way to seats aboard airliners. Given the stepped-up worldwide emphasis on tighter controls to deter terrorists, the tests bared gaping holes in airport security in this country that demand more than a routine response.

Just as troubling are the inspectors' conclusions that the Federal Aviation Administration was, in the words of Inspector General Kenneth Mead, "slow to take actions necessary to strengthen access control requirements and adequately oversee the implementation of existing controls." The FAA has replied that it already has been vigorously addressing the problems. But the agency's actions alone won't do. The federal government, airlines and airport managements need to rethink their collective approach to security.

Investigators reported that "piggybacking"--following authorized employees through doors and gates--was the most successful method of entry. But they also found unguarded elevators and--once on board aircraft--dozens of instances in which no one was there to challenge them. In still other areas, the investigators deliberately set off 25 emergency exit alarms; in 10 instances security personnel never responded.

Since these tests, the FAA says it has been running thousands of its own unannounced tests and taking enforcement actions. Cathal L. Flynn, the agency's associate administrator for civil aviation security, has written to airport industry officials outlining new security proposals and procedures. But as it stands, airports and airlines for the most part operate their own systems and do their own hiring of security personnel. Training is neither uniform nor adequately reinforced. Some professional force should be created, if not directly under the federal government then held to more strict federal procedures and continuing training.

Air travel remains remarkably safe in this country but terrorism has become more sophisticated and less readily detectable. Lax security is never acceptable. Tighter security requires far more professionalism than it enjoys today.