Airlines serving the Washington area began dusting off contingency plans yesterday for keeping as many airplanes in the air as possible if controllers go ahead with their threat to strike at 7 a.m. Monday.

Most executives declined to discuss specifics of their airlines' emergency plans. But many expressed confidence that the Federal Aviation Administration is now better prepared to keep traffic moving than it was six weeks ago, when controllers came close to walking off the job.

At that time carriers publicized elaborate contingency plans to cancel up to two thirds of all commercial flights in and out of Washington. Some actually accepted bookings for emergency flights, which never took off.

Yesterday, executives at many airlines caucused on ways to handle the strike and waited for guidance from federal officials.Most stressed that final decisions on flight cuts would have to wait until Monday, when it would be clear how many, if any, controllers would strike.

While many executives were very cautious, spokesmen for some airlines appeared to be less alarmed than before, expressing hope that even with a strike most passengers eventually could be sent to their destiantions by combining flights and juggling schedules.

For example, a U.S. Air spokesman said that passengers "holding confirmed reservations should plan to travel and they should be able to get on other flights if necessary in the event of a strike."

June Farrell, spokesman for Eastern Airlines, predicted that "the bulk" of its 90 flights daily in and out of National Airport would continue to operate. The airline would attempt to notify passengers in advance if flights would be affected, she said.

United Airlines spokesman Joe Hopkins said that "we are just booking our normal schedule right now."

Rules established by the Professional Air Traffic Controllers Organization (PATCO) require that 80 percent of all controllers in the union's jurisdiction vote to strike. Voting is to begin at midnight Sunday night, with results expected early Monday morning.

According to Federal Aviation Administration official Robert Throne, "flow control," or a general slowdown of regular schedules, would probably be implemented on the first day of a strike, while the FAA took stock of how many controllers were out.

In recent weeks, the agency has worked out plans for carriers voluntarily to reduce their operations by 25 or 50 percent during flow control. Many executives said this refinement was a marked improvement over previous plans and would facilitate service during a strike.

The FAA could also move from flow control to special emergency contingency plans. In a worst-case scenario, with only supervisors at the controls, about 8,700 of the nation's approximately 14,200 scheduled flights would fly on the plan's first day, he said.

Depending on how many controllers continued to work and if wrinkles could be smoothed out, remaining commercial flights and then flights by private aircraft could be added, Throne said.

Cutbacks under emergency contingency plans would hit much harder at commuter airlines than trunk carriers. Ransome Airlines, the largest of the 11 Allegheny Commuter airlines, said it would have to cancel all of its 19 daily flights between Philadelphia and National Airport.

Meanwhile, train and bus lines were reexamining plans devised during the last strike threat to lay on extra service to accommodate any overflow from the area's airports.

In the event of strike, Amtrak plans to put into service all available passenger equipment, adding about two passenger cars to each scheduled train in the Northeast corridor, according to Jung Ha Lee, an Amtrak spokesman.

Greyhound and Trailways plan to have extra buses and operators standing by to add extra trips if passenger loads demand.

Car rental agencies, expecting that many travelers would turn to them for short-distance trips, said they would move cars and personnel away from airports to downtown facilities. They expected an increase in one-way trips.