If you live near or beyond the Capital Beltway, Dulles and Baltimore-Washington international airports are, in many cases, about equally convenient to reach by car. But Washington National is still the airport most travelers can get to fastest.

Those are some findings from the AAA's Great Airport Race yesterday. The American Automobile Association's Potomac Division, at the request of the promotional Committee for Dulles, dispatched 18 drivers from six locations in the region at 7 a.m. One driver was sent from each location to each airport. Parking and walking time at the airport were included in the figures.

Not surprisingly, according to AAA spokesman Tom Crosby, National was the most convenient overall; the average travel distance was 12.5 miles and the trips averaged 36 minutes at an average speed of 21 miles an hour. Comparably, for Dulles, it was 31.8 miles, 52 minutes and 37 mph. For BWI, it was 38.5 miles, 54 minutes and 43 mph.

From Wheaton Plaza, however, a trip to National took the longest: 52 minutes. That compared with 46 minutes to Dulles and 44 minutes to BWI. From 18th and I streets NW in downtown Washington, the National trip took 17 minutes, Dulles 43 minutes and BWI 48.

A similar race was driven in the evening rush hour, with results to be tabulated later.