Top officials for Continental Airlines said yesterday that a substantial number of its striking mechanics were returning to work and that the airline was fulfilling its pledge to operate 85 percent of its schedule.

Furthermore, leaders of the International Association of Machinists and Aerospace Workers (IAM) conceded in background interviews that Continental's plans to continue flying were working well at this point. The union, which represents 2,000 of Continental's 13,000 employes, struck at midnight Friday after negotiations broke down.

This strike is regarded by aviation labor experts as a potential watershed dispute because of Continental's strategy of attempting to fly most of its schedule and hire replacement employes to take the jobs of strikers. Continental is one of several airlines showing heavy losses as a result of the recession and competition from new airlines spawned by deregulation.

Other airlines, including Eastern and Republic, have settled with the machinists this summer to avoid a strike, then sought new concessions after signing a contract.

Continental is executing a detailed plan to keep flying despite the strike. Seventeen cities, none of them essential to Continental's primarily western network, were trimmed from the schedule. The airline says that it is operating its remaining schedule without a loss of passengers.

Since the strike began, cabin cleaning and kitchen assignments have been contracted out to other firms on a long-term basis, and 800 Continental employes represented by the IAM have been "permanently replaced," Continental spokesman Bruce Hicks said.

Supervisors and contract mechanics, as well as union mechanics choosing to ignore the picket lines, are maintaining the airplanes. The Federal Aviation Administration said it was conducting special surveillance of Continental to ensure that safety standards are met.

Neither union nor management officials would estimate how many union mechanics were working despite picket lines. Hicks said the number was "substantial," but union sources said many mechanics who initially had ignored the picket lines were having second thoughts.

Union spokesman James Conley said, "There is no doubt in our minds that this is a classic case of union-busting." When a 30-day federally ordered cooling-off period expired at midnight Friday, the company posted its own work rules and salary schedules.

The IAM needs friends if it is to turn the situation around. The Air Line Pilots Association decided Sunday night to continue flying the airplanes but to keep its options open.

The IAM has not sought support from the Union of Flight Attendants because, an IAM source said, "Continental has trained 800 other flight attendants. Until we have shown our strength, there is no reason to jeopardize their membership."

"One weekend plus one day isn't a test," the source said.

Union and management officials yesterday agreed to meet in Houston with the National Mediation Board this afternoon to see if there is any reason to resume talks.

A split within union ranks is working to management's advantage, both sides agreed. Continental, a subsidiary of Texas Air Corp., merged last October with Texas International, which ceased to exist. In many cases, former TI mechanics are working while former Continental mechanics are not.

Continental is paying mechanics $16 an hour under the work rules it posted at 12:01 a.m. Saturday, when the strike began. This is the same rate Continental was paying its Texas International mechanics, and $2.55 an hour more than it was paying mechanics who initially worked for Continental.

However, mechanics now can be shifted from station to station instead of being held, sometimes when there is no work to be performed, at the same position, Continental officials said.