Striking pilots at United Airlines delayed a back-to-work vote yesterday because of problems that arose for 8,000 flight attendants who walked off the job in support of the walkout, according to the Air Line Pilots Association.

United spokesman Chuck Novak said "we are still optimistic about an early return" to work for the members of the Association of Flight Attendants and for the 5,000 pilots, who went on strike May 17.

But ALPA spokesman Don Skiados said "we have made clear all along that we are not going back until all issues are resolved" for the attendants' union, 80 percent of whose members have supported the strike.

"They are hung up about seniority," Skiados said, referring to yesterday's lengthy negotiations between United and the attendants' union at a Chicago hotel. The problem centers on proposed reassignments and seniority credit for the 8,000 striking attendants versus the 2,000 who remained on the job, union sources said.

Novak said United was hopeful that both unions would settle by the weekend and that the airline could resume full service next week.

New details emerged yesterday about the pilots' proposed two-tier pay scale, which provides considerably lower pay for new hires. ALPA sources said that, under the proposed settlement, a newly hired pilot would start at $21,600 a year instead of the current $22,452.

The gap would widen dramatically after the first year. A fifth-year pilot at United currently earns $60,456; under the proposed settlement, a new hire would earn $27,792 in the fifth year, or 54 percent less than now.

United and ALPA had clashed over how long the dual pay scales should exist. United sought a 20-year term, but the tentative settlement calls for arbitration on this point after five years.

Once the pay issues were settled May 24, back-to-work issues held up a settlement. United and the pilots resolved the problem by agreeing to allow U.S. District Court Judge Nicholas Bua in Chicago to rule on whether United can assign higher seniority rights to employes who did not strike.

ALPA said it would delay a vote on accepting its tentative settlement until the flight attendants' talks have concluded. Details on those negotiations were not available last night.

ALPA's 30-member United executive council, which must vote on the proposed settlement, has reviewed the contract and is likely to accept it if the attendants settle, union sources said.

ALPA said that, if the strike lasts a few more days, it will begin paying $1,800-a-month strike benefits to 570 newly trained pilots who refused to work for United once the strike began. As part of the proposed strike settlement, Judge Bua is to decide whether the union can demand that United hire the new trainees.