DALLAS (August 10, 2012)—David Bates, the head of the pilots' union at American Airlines is resigning after pilots rejected a contract offer he supported.

Bates said Thursday that the union's board asked him to resign and he agreed.

Bates supported ratification of a company offer to give pilots pay raises and a 13.5 percent stake in the company after it emerges from bankruptcy protection, but 61 percent of pilots voted to reject the offer, which contained outsourcing provisions they opposed.