The number of flights at Washington's National Airport will increase soon by about 7 percent under a decision announced yesterday by the Federal Aviation Administration.

The agency said it was removing National from the list of 22 airports whose operations have been restricted since last August, when the firings of the striking air traffic controllers forced cutbacks in nationwide air service. The number of flights at National will still be controlled, but by the government's metropolitan airports policy instead of by the air traffic control-induced restrictions.

As a result, the number of hourly flights--both takeoffs and landings -- by the airlines will be allowed to rise to 37 each hour between 7 a.m. and 10 p.m., for a total of 555 operations a day. By comparison, the FAA said yesterday that there were 521 flights at National on Tuesday, a level that would allow an increase of 34 flights.

Who gets what at National will be decided by representatives of the airlines, who will begin discussions at a meeting scheduled for Monday. Because National is a popular and money-making airport for the airlines, agreements in the past have been difficult to achieve.

The change in National's operations was part of new FAA regulations on the allocation of additional landing rights to be made available at the 21 airports that remain under the air traffic restrictions. The FAA said it will distribute more than 1,100 additional slots -- as landing rights are called -- to the airlines in late October as newly trained controllers begin entering the work force.