Boeing machinists are deciding whether to accept a contract that would concede some pension and health care benefits in order secure assembly of the company's new 777X airplane in Washington state.

The offer has fractured the union and drawn unusual pleas from politicians who say the deal is necessary to support the Puget Sound region's economic future. Boeing has been exploring the prospect of building the 777X elsewhere, and that could trigger a steady exodus of aerospace jobs from a region where Boeing was founded.

Local union officials are urging their 30,000 members to oppose the deal, arguing that the proposal surrenders too much at a time of company profitability.

Voting will to take place from 5 a.m. to 6 p.m. today. Results are expected to be announced later in the night.