Machinists at Boeing's combat aircraft facilities have voted to strike from 4 August, rejecting the company's revised contract offer despite improved pension terms.

Boeing is preparing for a major strike at its St. Louis-area defense factories. The move comes after union members rejected the company's revised contract offer. The strike will see some 3,200 machinists walk off their jobs starting midnight today. This is the first such action since 1996 when a similar strike lasted for 99 days.

More than 3,200 union members who assemble Boeing's fighter jets in the St. Louis area and Illinois went on strike on Monday after rejecting a second contract offer the previous day. Boeing Defense said it was ready for the work stoppage and it will implement a contingency plan that uses non-labor workers.