Union representatives at Eastern Airlines reacted angrily yesterday to Eastern Chairman Frank Borman's ultimatum that, unless they accept a 15 percent pay cut by Nov. 1, he will follow Continental Airlines' lead and reorganize his troubled company under the protection of a bankruptcy court.

While Continental's employes and former employes complained about dramatic pay cuts and disappearing jobs, Continental resumed domestic operations yesterday on a dramatically reduced schedule with bargain-basement fares and few passengers.

With one major airline already in bankruptcy and another threatening to follow, there were these other developments yesterday:

* The Air Line Pilots Association (ALPA) scheduled a meeting of its master executive council at Continental Wednesday night to vote on a possible walkout. The pilots charged that Continental's new work rules raise serious safety questions. The Federal Aviation Administration said it is monitoring the Continental situation closely.

* ALPA President Henry Duffy said he is willing to discuss the Eastern situation with Borman. "Nobody more than us could want that company to return to profitability," he said. "We've said all along that, when somebody tells us their company is in trouble, the first thing we want to do is verify that it's so. When verified, we'll do everything we can to help."

* Continental spokesman Bruce Hicks said the airline flew "all but eight or nine" of the flights it is planning to operate on its reduced schedule, and those not flown will be flown today. Although early flights had as few as six passengers on them, by mid-day loads had reached 68 percent in some cases, Hicks said. Continental was charging $49 a seat for flights to Houston and Denver; $98 to many other domestic cities served by the carrier.

Eastern resumed negotiations on a new contract with its flight attendants. A federally ordered 30-day cooling-off period will expire at midnight Oct. 12. "We cannot be intimidated by threats," said Patricia Fink, president of the 5,800-member Transport Workers Union, which represents the flight attendants. The union seeks a 33 percent pay increase over three years.

Eastern, the nation's fourth-largest carrier in terms of revenue passenger miles, lost $106 million during the first seven months of the year after sustaining a net loss of nearly $75 million in 1982.

Borman's ultimatum was delivered on Monday to Eastern's 37,500 employes by videotape. "He told them we have three choices," said Richard McGraw, Eastern's senior vice president for corporate communications. "One is to shut the airline down, one is to file a Chapter 11 bankruptcy petition and try to operate like Continental Airlines, and the only really viable option is to approve a 15 percent wage cut."

Airline analyst Robert Joedicke of Lehman Brothers Kuhn Loeb said the fact Continental is seeking to eliminate existing labor contracts and reduce its schedule under bankruptcy law protection adds credence to Borman's threat at Eastern.

"Continental is taking a bold and daring, but dangerous, move," Joedicke said. "One doesn't know whether it will succeed or not."

Charles Bryan, president of the 13,000-member machinists' union at Eastern, said "we've done extensive research at Eastern Airlines and they're not about to go bankrupt. The only reason they would go bankrupt is if they did it the same as President Francisco Lorenzo at Continental, to destroy the unions. The company is not in that bad shape."

Union leaders also criticized Borman for spending money on new airplanes such as the Boeing 757 in a time of financial difficulty.

Eastern spokesman Tom Myers refused to discuss the unions' reaction to the videotape. As for the 757s, he said "we need the aircraft for their fuel efficiency and their low operating costs. We've got them ordered, and it would be more costly to cancel the orders than to take them."

Meanwhile in New York, Standard & Poor's Corp. said it lowered its ratings on Eastern's secured equipment certificates and also lowered the credit rating of the Dade County (Fla.) Port Authority, which runs Miami airport where Eastern is the prime carrier.

Continental started this all when it filed for bankruptcy Saturday night, reduced its employes from 12,000 to about 4,500, cut some of their salaries as much as 50 percent, and reduced the number of domestic cities served from 78 to 25.