DALLAS — The leader of the pilots union at American Airlines resigned after pilots rejected a contract that he supported. David Bates said Thursday that the union’s board asked him to resign.

The company had offered pilots pay raises and a 13.5 percent stake in the company after it emerges from bankruptcy. Bates portrayed it as the best deal possible. But 61 percent of pilots voted to reject the offer, which contained outsourcing provisions they opposed.

American said it will ask a bankruptcy judge to impose terms of an April offer that included smaller pay raises and no stock in the new company.

Vice president Anthony Chapman was elevated to acting president.

Bates struck a firm but more conciliatory tone toward management than did his predecessor, Lloyd Hill.

American is seeking about $1 billion in annual labor-cost savings from pilots and other employees.