The Federal Aviation Administration ordered an emergency amendment to the security plans at U.S. airports late yesterday that will require background investigations for all airport, airline and contractor personnel who have access to airplanes and secure airport areas.

"Recent occurrences have demonstrated the need for this limited action to be taken," the FAA said in a telegraphed order to its regional directors. They will pass the order on to all airlines and airport operators as part of the agency's intensifying antiterrorist effort.

Additionally, a senior Transportation Department official said, the FAA will seek legislative changes so it can require more thorough background checks for airport employes than are now permitted under some federal and state laws. Legislation is also being considered that would make it a federal offense to illegally gain unescorted access to secure areas.

"We have found that while we can slap a fine on people who have responsibility for the security programs -- the airports and the airlines -- we don't have the authority to fine somebody who illegally gains access," the official said.

The "recent occurrences" include the successful attempts of some CBS News employes or contractors to win employment in secure areas at Chicago's O'Hare International Airport and other airports after submitting inaccurate resumes, according to several sources.

Their ability to penetrate the system with a phony job application was explained to Deputy Transportation Secretary James H. Burnley IV by CBS journalist Mike Wallace, who taped a recent interview with Burnley on airport security for an upcoming segment of "60 Minutes."

The sources also said that inaccurate information submitted by some CBS employes or contractors had been detected in some cases and the people in question were not hired. "They had mixed success," one source said.

The House Government Operations subcommittee on transportation had earlier called for improved security of airport ramp and terminal areas. The senior department official said that "our look at this problem began with that report," but was intensified after the Wallace interview.

Regardless of the motivation, the two most highly publicized recent hijackings in the Mideast were likely made possible because weapons were stashed on the airplanes before their flights, not because they were carried through metal detectors.

That has focused attention on ground security of airplanes. A variety of people have access to planes, including food-service personnel, cleaners, and mechanics. Many of them are not airline employes, but employes of contractors, often working for relatively small wages. The same is true of employes who operate metal detectors and X-ray equipment to check carry-on baggage.

There has been some concern on the part of the industry that thorough background checks for minimum-wage employes would impose unrealistic costs.

At a minimum, the newly ordered background checks must include a check of references and prior employment histories. Procedures for such checks must be in place by Dec. 15 and would apply to anyone hired after Nov. 1 who has "unescorted access to any area . . . "

The Air Transport Association had no comment last night pending its review of the order.

The FAA said that it is "necessary that all employers assure that the background of such employes be checked to the extent necessary to assure that permitting them unescorted access to any area on the airport controlled for security reasons is appropriate."

FAA and airline security personnel are known to be concerned that publicity about hijackings and how they happen is providing too much specific information to the public. "We want to make sure we don't give people a diagram on how to rob a bank," one official said.