A ruling by a federal appeals court late Wednesday appears to have mortally wounded PSA's plans to acquire many of bankrupt Braniff International's airplanes and employes, but both Braniff and PSA said yesterday they would make one more try to keep the effort alive.

The three-judge panel in the 5th Circuit Court of Appeals in New Orleans sent the proposal back to federal district court in Fort Worth with the instructions that any Braniff-PSA venture be submitted as part of a full reorganization plan, a lengthy process that would require approval from a majority of Braniff's creditors.

The judges also ruled that the Braniff's former takeoff and landing rights, or slots, were not property per se, and thus would not automatically belong to PSA. That was a ruling sought by the Federal Aviation Administration, partly because it has reallocated 350 of Braniff's slots to other airlines.

Braniff said yesterday it will appeal the panel's decision to the full 5th circuit. If it cannot get a reversal by midnight Saturday, however, the deal with PSA is dead, both Braniff and PSA said, and Braniff would face normal bankruptcy liquidation proceedings.

Nonetheless, PSA spokesman Cecil Scaglione said, "If the Braniff folks come to us in four days, four weeks, or four months with another deal, we'll listen. It's just that this particular transaction expires tomorrow midnight. We hold little hope."

PSA, a strong West Coast airline, had hoped to start a Texas Division based in Dallas.