Workers at Burnley’s Aircelle aerospace company struck on Monday following a half-day strike on Wednesday of last week over pay.
They are angry with the offer of a below inflation 2.5 percent rise.
They have also banned overtime and more strikes are expected in coming weeks unless a solution is reached.
Dave Gorton, from the Amicus union, said staff are not only disgusted at the small pay offer, but also that contractors have been brought in on higher wages and loyalty bonuses.
Aircelle employs around 450 full timers at the Burnley site and more than 300 – virtually the entire trade union membership – took part in the strikes.