“Definitely the loss of that pension is still there right at the heart of this for many,” said Jon Holden, the president of the International Association of Machinists and Aerospace Workers District 751, after members voted down the company’s latest offer last week.

The union says Boeing pushed members to give up their pension plan in 2014, in part by threatening to move production of new planes elsewhere if they didn’t. The company replaced that pension with a 401(k) retirement plan. A decade later, many workers still feel cheated.