Federal Aviation Administration officials, concerned about reports that Eastern Air Lines was deferring maintenance on too many airplanes, said today they are in the midst of an intensive safety investigation of the carrier.

The inspection at the nation's third largest airline began early in December and is expected to continue for another two or three weeks. More than 25 FAA inspectors are involved full time.

"We have not seen any serious safety infraction that would require that we take drastic action at this point," said William M. Berry Jr., manager of the FAA's Southern Region flight standards division. "We are seeing some deficiencies that we are still investigating; we don't know how large they are."

Frank Borman, Eastern's chairman and chief executive officer, said in an interview Wednesday that he welcomed the inspection. "Sure," he said, "they will [find some deficiencies] -- not much, though . . . ."

Borman said the "ethic of safety first" exists at Eastern, but said that "doesn't mean that we're perfect and it certainly doesn't mean that a good inspection isn't going to find something wrong with us, but we have established procedures, we follow them, and we don't spare expense when it comes to safety . . . even when we're in financial trouble . . . ."

The inspection was started in response to complaints from passengers about flight delays and complaints from airline employes to FAA inspectors, Berry said. It began as an effort of the FAA's Miami district office, but was expanded and incorporated into a new agency program to thoroughly examine operations and maintenance practices at every major airline.

As a result of a similar inspection, American Airlines recently paid a record $1.5 million civil penalty to settle all FAA issues, although it denied any violations. The FAA has proposed civil penalty settlements of $700,000 for Western Airlines and $300,000 for Continental Airlines in safety-related cases.

"The customer complaints about Eastern, the observation of our inspectors when they ride in the cockpit and looking at the number of maintenance carry-over items that the airplanes were carrying led us to believe that maybe we need to look at that entire thing with some other eyes," Berry said.

"These airplanes are all designed with redundant systems and the concept of deferred maintenance is a part of the design of these airplanes," said Borman, a former astronaut. "Right now, the shuttle -- the space shuttle -- they're running off with deferred maintenance items that are around 100 to 200 per trip because they have the same design philosophy . . . ."

Berry said Eastern "is being very cooperative. We have no reason to believe that what we see at this point is related to any labor problems or money problems," both of which face Eastern today.

Berry said the airline has a good supply of spare parts and a sophisticated computer delivery system. "We just have not come up with the causes of delays," he said.