At the 11th hour yesterday, the Department of Transportation put off release of an interim plan to allocate the limited access to Washington National Airport among the 23 airlines seeking the right to operate there during the busy holiday season, sources said yesterday.

The delay could jeopardize planning for the Christmas and New Year holidays. It also means the airlines will miss an Oct. 21 deadline set for the inclusion of holiday schedules in the Official Airline Guide, the document most used by airlines, travel agents and others for booking flights.

Last night, Thomas Allison, DOT general counsel, said the department had decided to seek public comment on the National allocation question before issuing any definitive plan and that, in fact, no plan had been approved by Transportation Secretary Neil Goldschmidt.

However, before the last-minute change in plans, sources said the department was ready to issue an interim formula allocating access to National that paved the way for the start of significant new low-fare air service between Washington and New York's LaGuardia Airport by New York Air, a new affiliate of Texas International Airlines.

Allocations for slots -- the industry term for the number of takeoffs and landings permitted at the airport -- were settled through the end of November by the airlines themselves. For the past 12 years, a committee comprised of the airlines has been allocating slots at airports where they are limited, with the government's blessing. But the airlines, after trying for weeks, were unable to come up with a formula that allocated flying hours for the period between Dec. 1 and April 26, and turned the task over to the DOT last week.

In the plan discarded at the last minute yesterday, the DOT would have used as a base the allocations the airlines had agreed to through November. Then four slots would have been taken away from Eastern Airlines, the largest single operator at National with 128 slots (extra sections of the Shuttle are not included), and from USAir, with 84 slots. Two slots also would have been taken from each of the 8 airlines with more than 20 slots. The resulting 24 slots would have been given to the new entrants -- 18 to New York Air, 4 to Air North and 2 to Midway Airlines, which started service at National earlier this year.

The DOT would have set aside one slot in each airport operating hour and two in the peak hours for the new services, and the airlines would have picked them according to a formula. In deciding which hourly slots the 10 incumbent airlines would give up, the airlines would have been ranked in order of their remaining slot holdings with the ones hurt the most choosing first which hours to give up.

DOT general counsel Allison said that a public-comment period was decided on after some airline representatives conveyed their views to the department. It seemed appropriate to allow all carriers to make their views known, he said. "There also might be some ideas out there that might be worth incorporating in an emergency interim plan," he said.

The period of public comment will be short, ending next Thursday, with the comments analyzed and options for Goldschmidt ready by the following Monday so that a decision can be issued that week, Allison said.