Negotiations on a proposed joint airline venture between Braniff International and PSA Inc. collapsed yesterday after Braniff's pilots refused to go along with future seniority rules sought by PSA.

The proposed venture could have put as many as 1,500 idled Braniff workers back to work and 25 to 30 of the grounded airline's planes back in the air.

Failure to reach agreement with the pilots meant that Braniff couldn't meet a Tuesday midnight deadline set by PSA's directors for the delivery of signed labor agreements from Braniff's pilots, flight attendants, flight dispatchers and Teamsters' union.

Braniff, which suspended services May 12, had gotten signed agreements with the dispatchers and Teamsters and was finalizing an agreement with the flight attendants but could not get its pilots to sign on the dotted line.

The pilots had agreed to the terms of a new contract outlining new lower wage scales, work rule concessions and scheduling during the period covered by the joint venture. But the pilots balked at seniority provisions required by PSA should the California-based airline elect later, as would be allowed under its agreement with Braniff, to acquire Braniff's interest in the venture and merge the venture with PSA. In the event of such a merger, the seniority provisions would have placed Braniff employes behind those PSA employes already on board when the joint venture started.

"By not accepting the PSA provision on seniority, the Braniff pilots have denied themselves 370 jobs now and, at this point, have denied over 1,500 other former employe jobs as well," Braniff Chairman Howard Putnam said yesterday.

"Seniority is a very, very important thing in this industry," said Dick Goduti, a member of the Air Line Pilots Association master executive council, after collapse of the PSA-Braniff deal. He said the pilots had negotiated away 60 percent of their salaries and made other concessions "in an attempt to get the airline off the ground, which we wanted to do."

But in the event of a merger, he said, "we did feel, for what we were putting into it, that we were entitled to participate on an equal footing" with PSA pilots.

PSA spokesman William E. Hastings said yesterday they were "disappointed" that the negotiations were terminated, but felt that the seniority issue was "not a negotiable item as far as PSA is concerned." He said PSA had reached agreements with its unions regarding seniority in the event of a potential future merger and was not willing to renege on them.

Putnam said yesterday that Braniff will continue its efforts to reorganize in an attempt to provide its creditors, stockholders and former employes something more than a liquidation would yield them. When negotiations with the unions and PSA looked promising, Braniff was given until Jan. 4 by the federal bankruptcy court to work out a reorganization plan.

PSA's deadline didn't include an agreement with Braniff's machinists, who had walked out of earlier negotiations on the seniority issue. A hearing in bankruptcy court was scheduled for Nov. 29 on Braniff's request to dissolve its contract with the machinists union.