A wide majority of Delta Air Lines Inc.’s pilots rejected a new three-year contract that contained big pay raises, the Air Line Pilots Association union said Friday, dealing a setback to an airline that has enjoyed unusually strong labor relations.

Of the 10,700 pilots who cast ballots, 65% voted against the deal compared with 35% who cast ballots for the agreement. Union leaders reached the tentative pact with management last month. It would have superseded the aviators’ current labor contract, which isn’t open for renewal until year end.

One point of contention was a change in the terms of the profit-sharing plan.

Delta declined to comment Friday.