"NATIONAL AIRPORT is so dangerous, it's safe." That's what an aviation safety expert said recently to Post reporter Douglas Feaver. He explained that the landing approach down the Potomac River is so tricky that pilots never take it for granted. Thus, one of the cause of airplane accidents -- pilot inattentiveness -- is eliminated.

To aviation buffs, that may be an encouraging analysis of what goes on in the air around the nation's 10th-busiest airport. And it may help explain National's enviable safety record -- no fatal accident since 1949. But as airliners and electronic landing systems get better and more complex, does it make sense to continue to stake so much on the ability of pilots to wend their way down that curving approach over the Potomac River Bridges?

The question arises now because of the proposal of the Federal Aviation Administration to open National to bigger and, it is claimed, quieter jets. The Air Line Pilots Association says it has doubts about the safety aspects of flying these planes in and out of that airport. But the FAA believes there will be no safety problems.

We haven't seen enough evidence yet to form an opinion on the ALPA's assertions. But there is an obvious conflict of interest here that is disturbing. The FAA is the final arbiter of the safety of airports. It is also the operator of National Airport. That means the FAA must decide whether its own proposal meets its own standards for airport safety.

In some situations, that conflict might be little more than routine. But this time, the FAA is being pressured by many members of Congress to permit as many pasengers to use National as can be crammed into it. The FAA is also being pressured to reduce the noise made by the airplanes that use those runways. Letting bigger jets into National provides a tempting answer to those competing pressures -- more passengers can travel in fewer and quieter big planes. But whether the FAA can pull off this solution depends upon whether the FAA decides the big planes can be operated safely there.

The situation is somewhat analogous to that which led to the breakup of the old Atomic Energy Commision. It was finally understood that the AEC's dual roles of promoting the use of atomic energy and ensuring it was used safely put the commission into a perpetual, and often difficult, internal conflict. Could the same thing be happening to the FAA with its legislatively imposed roles of promoting aviation, ensuring aviation safety and operating two major airports?

Congress could eliminate this conflict by getting the FAA out of the business of running airports and repealing the mandate of the agency to promote aviation. National and Dulles airports could be operated just as well by some other federal agency or, even better, by a regional or state authority. That might not have a direct impact on the airports' safety records, but it would remove one presistent question: does the FAA's prime interest at National lie in overseeing the safety of what happens there or in providing a convenient airport for members of Congress who oversee the agency's budget?