A federal appeals court today turned down the request of Northwest Airlines and four other carriers to overturn the Department of Transportation's plan for allocating access to Washington's National Airport after Dec. 1.

The court's denial removes one of the hurdles that could have delayed the start of New York Air's proposed low-fare service between Washington and New York scheduled to begin on Dec. 14, as well as expanded services by other airlines new to National Airport.

The ruling by a three-member panel of the Eighth Circuit Court of Appeals came several hours after an oral argument during which attorneys for the DOT and New York Air defended the DOT's plan against the attack of Northwest and other airlines forced to reschedule or cancel flights because of the emergency plan.

Thomas Allison, DOT general counsel, argued before the court that most airlines operating at National already had adjusted their schedules based on the DOT plan outlined on Oct. 30 and that changes now would "create more havoc and chaos and passenger disruption and inconvenience" during the Christmas holidays than granting Northwest and the others the relief they sought.

The airlines challenging the DOT plan wanted the court to stop the DOT from forcing them to relinquish the slots -- takeoffs and landings -- they are using in November.

Allison disputed the airlines' contention that they and their passengers would be irreparably harmed, arguing instead that the airlines seeking to overturn the DOT plan generally are larger carriers -- Northwest, Pan American, American, Braniff, and Air Florida -- that could make the "relatively small adjustments" required by the plan. "It doesn't strike me as a terrible burden," Allison said.

"On the other hand, issuing a stay would be putting some carriers out of business, or at least not allow them to get started until they get slots," he said, which would be contrary to the precompetitive mandate of the Airline Deregulation Act. Gerry Levenberg, New York Air's attorney, told the court the airline already had spent about $2 million in preparation for the new service and was training hundreds of new employes.

In his presentation, Allison also aruged that a court decision favorable to the challenging airlines would treat slots as property rights.

"I have difficulty with that," he said. "No carrier has any slots after Nov. 30. As of Dec. 1, New York Air has as much right to those slots as Northwest or Pan Am or Eastern." Eastern, the holder of the largest number of slots at National, didn't like the DOT plan but had told the court it did not want to have to change its schedule any more.

The DOT got into the slot allocation business when the airlines themselves told the agency they had reached an impasse and by themselves could not come up with a formula for allocating slots at National after Nov. 30.

Ronald Eastman, Northwest's attorney, told the court the DOT easily could let Northwest and the other four airlines have the additional slots they wanted -- and let New York in -- by abandoning its rule limiting major carriers to 40 slots an hour, at least during the holiday period, a rule Eastman said isn't enforced anyway.

"Really, the biggest fiction in the case is that DOT limits operations to 40 per hour. They do not," he said. He cited both the extra sections allowed the airlines -- like Eastern's Shuttle -- that don't count in the total and the airport's policy to let in as many private planes as want to land during good weather.