In the wake of Delta Air Lines pilots’ vote to reject a proposed labor contract, the head of the Delta pilots union said he will resign.

It’s rare for pilots to vote against a labor deal brought to them by union leadership for ratification. It can signal a disconnect between the union heads and the desires of the rank-and-file, and thus can lead to a shakeup in the union’s leadership.

The master executive chairman of the Air Line Pilots Association at Delta, Mike Donatelli, wrote a memo to Delta pilots saying he made the decision after “careful and thorough consideration.”

“It is time for the pilots of Delta Air Lines to unify,” he wrote. The move comes amid a two-day meeting of the union’s leadership to determine its next step and reassess its strategic plan.

The union’s leadership plans to hold another meeting in early September to elect a new chairman, who would step into the role to replace Donatelli Sept. 15.

The proposed labor contract for Delta pilots proved divisive, offering immediate pay raises of 8 percent along with other terms some pilots disliked, including a reduction in profit sharing and increased productivity requirements including changes to the sick leave policy.

Of the ballots cast in voting that ended earlier this month, 65 percent of Delta pilots were against the tentative labor agreement and 35 percent were in favor of it.