Boeing made an improved offer last month that was described as its "best and final," but union members say that wasn't enough.

Boeing and its largest union, the International Association of Machinists and Aerospace Workers (IAM), continued contract negotiations today after 25 days of strike action involving 33,000 U.S. West Coast factory workers.

Boeing's union has the aerospace company over a barrel. Boeing can afford to raise wages but only at the cost of a big cut in profits.