The Federal Aviation Administration announced contingency plans yesterday to cancel thousands of airline flights a day nationwide if Congress and the administration fail to reach a budget agreement by Oct. 1.

Without an accord, the FAA would be forced to furlough air traffic controllers, and while the furloughs would solve funding problems, they would reduce the capacity of the air traffic control system by about 25 percent.

The FAA plan would affect 41 major airports, including National and Dulles here. It sets hour-by-hour quotas for each airport, ordering each airline to cancel a specific number of flights. Individual airlines must decide which flights to cancel.

National Airport would be severely affected, with cancellation of 88 departures and 72 arrivals throughout the day. The cutback includes a few general aviation operations, but most of the cancellations are commercial airline flights.

Dulles was barely affected with five departures to be canceled in the hour after 9 a.m., and three arrivals to be canceled between 3 p.m. and 4 p.m. Baltimore-Washington International Airport was not included among the 41 airports listed.

The FAA, unlike many other federal agencies, provides high-profile, 24-hour-a-day services for the public, and its administrator, James B. Busey, has been among the leaders of a chorus of Bush administration warnings about the effects of automatic cuts under the Gramm-Rudman-Hollings deficit-reduction law if a budget agreement is not reached by Oct. 1.

As late as last Thursday, Busey said there was no way to avoid chaos on Oct. 1, with the FAA's Central Flow Control Facility placing immediate limits on operations and airlines scrambling to herd passengers to destinations.

However, the detailed plan released yesterday apparently will give airlines time to develop contingency schedules that would mitigate the chaos.

The FAA cutbacks were based on the number of flights per hour that a reduced air traffic control work force could handle. FAA officials said 6,000 operations a day would be affected at the 41 airports, counting airline flights, commuters and general aviation.

The impact, however, would be far more widespread. For example, although BWI is not listed, numerous flights scheduled to and from affected airports would be canceled. This ripple effect would lead to major traffic disruptions at all airports.

International flights by foreign airlines would not be affected although international flights by U.S. airlines would be controlled. However, Stan Matthews, the FAA's assistant manager for systems management, said that because of complaints from airlines, "that may be one of the things we will modify."

Individual airlines did not receive the plan until yesterday, and those contacted reserved comment. However, Robert J. Aaronson, president of the Air Transport Association, which represents major airlines, said the cutbacks would be "terribly disruptive." ATA spokesman Steve Hayes also complained that the FAA quotas produced differing numbers of arrival and departure cancellations, as at National Airport, which he said will lead to confusion. "We feel it would be much simpler and more manageable if the system were based only on arrivals," he said. "Then the departures would take care of themselves."

In addition to National and Dulles, the airports affected are Albuquerque, Atlanta, Boston, Bradley (Hartford, Conn.), Charlotte, Chicago Midway, Chicago O'Hare, Cincinnati, Dallas-Fort Worth, Dallas Love Field, Dayton, Denver, Detroit, Fort Lauderdale, Houston Hobby, Houston Intercontinental, Indianapolis, Los Angeles, Memphis, Miami, Minneapolis, Nashville, New York Kennedy, New York LaGuardia, Newark, Orlando, Philadelphia, Phoenix, Pittsburgh, Portland (Ore.), Raleigh-Durham, Salt Lake City, San Diego, San Francisco, San Jose, Santa Ana, Seattle, St. Louis and West Palm Beach.