The airline industry, uncertain how many planes it can get off the ground Monday, called on President Bush yesterday to use his emergency powers to keep air traffic controllers on the job if automatic spending cuts are imposed by the Gramm-Rudman-Hollings deficit-reduction law.

The Federal Aviation Administration has announced plans to furlough each air traffic controller 2 1/2 days every two weeks if no budget agreement is reached, resulting in about a 25 percent reduction in the capacity of the national airspace system. The reduced controller work force would be forced to cut the number of planes it handles to ensure safe operation, causing delays and cancellations to ripple through the country.

The air traffic system dodged a potentially greater problem yesterday when the National Weather Service postponed a plan to close 250 weather-observing stations nationwide from 6 p.m. to 6 a.m., which would have shut down nighttime airliner service. A spokesman said the weather service had received permission from the Office of Management and Budget to temporarily reprogram money from other sources, keeping the offices open full time until Oct. 15.

"It's absolutely ludicrous to hold the air traffic system of this country hostage to a budget crisis," Robert J. Aaronson, president of the Air Transport Association (ATA), told reporters in releasing his letter to Bush.

Aaronson told Bush that in a 1982 budget snag, President Ronald Reagan used his authority under the Anti-Deficiency Act to allow essential employees, such as FAA workers, to stay on the job. Aaronson said air carriers are projected to lose $1.25 billion over the next year, and it is "vital to the welfare of the airline industry" to prevent major cutbacks in service.

Dave Swierenga, the ATA's vice president for industry data, estimated that if the air traffic cutback takes place Monday, the revenue loss for airlines would be $14 million to $20 million per day. On top of this would come other potentially major costs such as hotels and meals for passengers stranded at connection points.

The FAA will save about $3 million a day in operating costs through its cutbacks.

"That's a pretty impressive damage ratio," said Clark Onstad, senior vice president of Continental Airlines, one of a number of airlines struggling for profitability. "It's unconscionable."

Amtrak, the national passenger train service, said all its trains will continue to run Monday and "we're gearing up for the potential of getting displaced airline passengers," said spokesman Clifford Black. Extra cars and possibly extra trains will be added between New York and Washington, he said.

Amtrak is subject to the deficit-reduction cuts, but earns more than 70 percent of its revenue from passengers and can continue operations for some time before cutbacks are necessary.

Airlines said confusion and delays are inevitable Monday if the automatic cuts take effect. Jack Ryan, ATA vice president for air traffic management, said delays would begin at some airports early in the morning and grow to three to five hours later in the day. Many flights would be canceled or consolidated.

Under the FAA plan, hourly quotas would be imposed on 36 major airports including National and Dulles here. The FAA's central Flow Control facility in Washington then would assign delays on an airliner-by-airliner basis as the number of scheduled flights exceeds the quota. On Thursday, if there is still no agreement, a special schedule would be placed in effect with 3,000 flights per day fewer than normal.

Particularly hard-hit Monday would be New York's LaGuardia, Newark, Chicago's O'Hare, Atlanta, Dallas-Fort Worth and Los Angeles, Ryan said.

About two-thirds of the 50 air traffic controllers employed at National Airport picketed yesterday afternoon to protest furloughs.

H. Michael Brown, president of the local chapter of the National Air Traffic Controllers Association (NATCA), said that National is likely to be hardest hit of the airports in the Washington area.

"I predict we're going to be seeing the first delays first thing Monday morning," Brown said.

Staff writer Stephanie Griffith contributed to this report.