United Airlines was negotiating with its 8,000 flight attendants late yesterday in hopes of averting a strike that would ground the nation's largest passenger carrier the week of Thanksgiving.

Both the airline and the union, the Association of Flight Attendants (AFA), were advising travelers that there was the possibility of a strike beginning at midnight last night.

American Airlines and Trans World Airlines, United main competitors on domestic routes, reported they were being swamped with requests for reservations as air travelers attempt to make alternate arrangements. United already had an advance booking of 440,000 people for Wednesday through Saturday of Thanksgiving week.

Two other disruptive labor disputes in the nation's commercial transportation network are possible next week:

The Professional Air Traffic Controllers Organization (PATCO) and the Federal Aviation Administration (FAA) recessed discussions over a new contract yesterday. PATCO has announced that it plans to conduct "informational picketing" at most major airports including the three near Washington, beginning Monday. There will be no union-authorized or sanctioned air traffic slowdown, PATCO president John Leyden said. However, many aviation observers expect at least sporadic air traffic difficulties during the week.

Votes of Greyhound bus drivers on a new labor contract were being counted last night in Scottsdale, Ariz., by the Amalgamated Council of Greyhound Locals. The drivers, working without a contract since Oct. 31 voted by mail on the new proposal. A cials had no comment.

Greyhound spokesman said "no precipitous" action is expected regardless of how the vote goes. Union officials had no comment.

But the United Airlines situation was by far the most immediate not only for the nation but for the Washington area as well.

Both union and company representatives were meeting with the National Mediation Board, a federal agency. While a spokesman there expressed hope for a settlement, a spokesperson for the AFA said, "If I had a ticket on United, I'd try to find another flight."

United has 66 flights a day in or out of Washington National Airport, 28 at Dulles International and 30 at Baltimore-Washington International United carries 1.4 million passengers to and from National annually, making it the second largest carrier there in terms of passengers with 11.4 per cent of the total.

At Dulles, where long-haul flights connecting Washington with major West Coast cities begin and end, United carries 32.1 per cent of the domestic passengers and 25.5 per cent of the total.

United is a major area employer because many of its flight and maintenance crews are based here. According to a United Spokesperson, 699 flight attendants are based here among a total of 2,500 United employees.

Both the flight attendants and United spokesmen agreed that wages were not the central issue in negotiations. Sue Liebling, national strike chairperson for the AFA said the primary areas of concern are improved working conditions, including a more efficient system of sheduling attendants, and contract guarantees on the number of flight attendants that would be assigned to each kind of plane.

"On a DC-10 (jumbo jet) for example, the FAA requires five flight attendants," Liebling said, "but United schedules eight. We want tht eight to be part of the contract, so United will not be able to cut us back tothe FAA minimums."

Job security has become a major issue among airline employees as they see increasing airline emphasis on cost cutting measures in an era of reduced federal regulation of fares and increased fuel costs.

PATCO president Leyden emphasized repeatedly at a press conference yesterday that no slowdown or other disruptive action is planned as part of the picketing effort. PATCO has been without a contract since July 8; negotiations have been held sporadically.

Federal employees, which the 14,500 PATCO members are, cannot strike and wages are not an issue. The central question, Leyden said, it a PATCO demand that senior members be permitted to bid for available controller positions on a nationwide, rather than local, basis.

"We've got guys who have been trying to get out of the New York radar room for seven years and can't move," Leyden said. The New York operation is generally regarded as one of the two or three most demanding in the nation.

If the PATCO picketing does not bring progress on a new contract, Leyden said, the fact that the even heavier Christmas travel period follows Thanksgiving "has not escaped our board of directors."