THE SAD TALE of National Airport took another strange turn Wednesday morning. Its parking lots were suddenly full and there was no place for would-be passengers to put their cars. Except, of course, in those places reserved for the cars of employees and VIPs. No one was sure why this had happened. Maybe, one official suggested, people were beginning their Thanksgiving vacations early.

It is possible that he is right and this parking lot jam was a freak incident. But it is also possible -- and much more likely -- that this was only a hint of what is to come. If passenger use of National Airport is to grow by 20 percent, as the Department of Transportation has recommended, or by more than that, as the airlines want, something on the ground is going to have to give. The 275 new parking spaces scheduld to open by next spring won't come close to meeting the demand. Even opening up that VIP parking lot to plebeian use won't help much.

Additional parking can be provided, of course, at considerable cost. Or passengers could be forced to take the subway, a bus or a taxi by simply hanging out an "almost always full" sign. But even if the percentage of passengers using Metro increases dramatically, as airport officials hope, the odds are that Wednesday's surprise mess will become routine within the decade.

There is a better way: stop the growth of National in its tracks and begin to reduce its passenger load. This city is served by two other fine airports. They are situated so that parking lots could be built almost forever without having to turn to multi-story garages or parking decks over highways, railroads or a river.

Why not take advantage of those airports? Why not put the millions of dollars that will inevitably be spent at National for a new terminal and for additional parking -- if use of National continues to grow -- into opening up ground transportation to Dulles?

The problem of what will be done about National's congestion and its noise -- never forget the noise -- will soon be handed over to a new administration. It would have been educational, not to mention fitting, for some of the new leaders to have been caught in that mess around National Wednesday before they gain access to those convenient VIP slots.