An IAM official said the vote on Boeing's latest offer is scheduled Jan. 3, the Seattle Times reported.
District 751 in the Seattle area posted a message on its website Saturday urging members to reject the contract.
"Because of the massive take-aways, the Union is adamantly recommending members reject this offer," local officials said.
District 751 members rejected a previous contract offer Nov. 13. Boeing then announced it was considering manufacturing its 777X plane elsewhere.
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