If you are flying out of Washington, you can probably take any scheduled flight to any city despite the air traffic controllers strike because so many people are cancelling their reservations, according to travel agents and airplane personnel.

Although only about 75 percent of scheduled flights are taking off, some travel agents are even booking people on standby and telling them to wait at the airport for cancellations.

"We've had a lot of people calling up and asking, 'Did that flight go? Did this flight go?'" said an American Airlines ticket clerk at National Airport. "And when we twll them they went, they say, 'Oh no, I should have been on it.'"

Travel agent Cathy DiMeglio of Capital Travel Inc. said she's had little trouble finding airline seats for passengers. "There may be fewer flights but most of them are not full," she said. For instance, if you wanted to go to Chicago today, she said, it would be easy.

"TWA is sold out in both classes, both coach seats are available on United," she said. Passengers could also choose between two Eastern flights, she said.

"We are flying a lot of empty seats around," said Eastern Airlines spokesman Lee Bright. He said very few flights are canceled and very few are delayed. "We are doing everything we can to get people to resalvage their vacation plans."

Some destinations are off the map. Ozark Airlines has canceled flights into Mason City and Ft. Dodge, Iowa, for instance. Flights are going to Des Moines and Waterloo, Iowa, instead.

Far more flights are flying than people imagine, Bright said. Although the Federal Aviation Administration asked airlines to cut flights by 50 percent when the air controllers strike began last week, permission to fly additional flights has routinely been given.

Travel agent Maureen Rocks of Suburban Travel in Prince George's Plaza said cancellations are making it easier for people to find seats. Some are afraid their connections will be delayed or canceled, while others are nervous about flying with air controllers on strike, she said.

"I saw one lady who is going down next week to a convention in Miami," she said. "She's a bit afraid to fly normally, but with the strike she decided to take the train." Normal train seats were all booked, Rocks said, so the woman had to book a roomette. "It cost her $100 more."

Meanwhile, Rocks said, people wanting to travel to Fort Lauderdale today have a choice of three flights leaving from National Airport. DiMeglio said that even when flights are fully booked, "I'll get passengers on standby and tell them to wait at the airport. The chances of getting on are good because of high cancellations."

Travel up and down the Eastern Seaboard isn't difficult to arrange either, she said. "Eastern's shuttle to New York is still running. Out of Boston, only the 7:10 business flight in the morning has been canceled. The 9:30 flight is still going."

If you wanted to travel to the West Coast today, things didn't look much more difficult. "One of the two night flights out of Los Angeles to Washington isn't flying," DiMeglio said. "I had a couple of people who did go to the airport there and were stranded. I don't know what happened to them; maybe they're still there." But other than that, she said, "things are pretty normal."

But there would be a few problems if you wanted to fly to New Orleans on excursion fairs, as Rocks found out on Saturday when she tried to find a flight for two nuns. "The cheapest flights are from Baltimore-Washington Airport," she told them. "Unless you want to pay more from National, forget Sunday, forget Monday."

The only way to fly to New Orleans today, she said, would be on a night flight, changing planes in Atlanta. You would arrive in New Orleans at 12:29 Monday morning. She eventually booked them on a Texas International flight on Tuesday. There are seats open on four different flights on Tuesday, she said.

DiMeglio said passengers and travel agents should find it still easier to book flights in a few days time, when schedules are more concrete. "It's a little harder now because you can't see what the exact flights are," she said. On Saturday, she and other travel agents were telephoning individual airlines to make sure flights shown on their computers were, in fact, flying.

Eastern Airlines expects to publish a new schedule early this week.