By the time many of you read this column, I'll be flying over the nation's midsection out of National Airport to San Francisco.

The message this column relates--that it often is a lot more convenient to fly across the country out of National with a midcontinent connection than to go out to remote Dulles Airport--probably will outrage many Washingtonians, notably the misguided claque that wants to close National Airport rather than adopt a rational policy toward its continued existence. As a matter of fact, the last six times I've flown to and from the West Coast, I've contrived to use National because of its convenience and lower cost.

Please, I'm not oblivious to the noise pollution created by National. I've suffered through concerts at the old riverside Watergate, near the Lincoln Memorial, where circling, stacked-up planes repeatedly interrupted the music. I've lived for most of the last 22 years directly under or close to National's flight path. I once had a near midair crash directly over my house, so I'm not oblivious to danger.

But as long as National is there and the service it provides is both more convenient and cheaper than that at Dulles, I'll use it. (Since I now live in Arlington, the area's other airport, Baltimore-Washington International, is not a reasonable alternative, though it surely is for many living on the northern rim of our metropolitan region.)

Why am I using National, where nonstop flights are limited to 1,000 miles, instead of Dulles, built to be our region's chief long-haul transcontinental and transoceanic airport?

My flight today was scheduled out of National at 1:32 p.m. With a connection at Chicago, it should arrive in San Francisco at 5:20 p.m., local time.

I have neither a car I want to to park at $3 or so a day at either airport, nor someone to drive and drop me off.

To catch my 1:32 p.m. flight from National, I can leave my apartment as late as 12:10 by Metrobus and subway, for a combined fare of $1.50. For the same airline's comparable flight from Dulles departing at 1:02 p.m., I would have to leave my apartment at 10:40 a.m. for a 75-cent bus ride to Rosslyn and a $7.75 airport bus, with an hour to wait at Dulles. At the West Coast end of the trip, I'd save 17 minutes.

Returning from San Francisco in two weeks, the facts are tilted even worse against Dulles. I'll arrive at National at 6:36 p.m. on a Sunday and even though the subway will be closed for the day, I can take a cab for about $5.50 and be home by 7:15 to 7:30 p.m.

But suppose I arrive at Dulles on the same airline's comparable flight to that airport. It gets me there at 6:50 p.m. The next $7.75 bus I can catch for Rosslyn leaves at 8 p.m., arriving there at 8:45 and getting me home, with a roughly $2 cab fare, at 9 to 9:15 p.m.

Recapitulating: transportation cost to and from National: $7. Comparable cost to and from Dulles: $18.25. Additional net time to and from Dulles, about three hours round trip, with all the extras on the Washington end.

Much of the tilt of convenience toward National rests on ground transportation arrangements, in distance, time and cost. An airport 26 miles from downtown never will overcome the convenience and economy of one three miles distant. Rail rapid transit, often considered a solution, is a wistful mirage--a subject MetroScene will deal with at a later time.

If Washington or its region, rather than the federal government, controlled airport policy, perhaps I wouldn't be able to travel from National to the West Coast. But a comparable passenger making an identical choice can make a trip similar to mine, also via Chicago, from New York's "local" LaGuardia Airport rather than using a nonstop from the "long-haul" Kennedy Airport.

As for me, I'll take National over Dulles whenever a comparable flight is available, even if it means compromising principle.

Which I'm doing. Be back in two weeks.