Boeing has until Friday night to avoid a strike that would paralyse its commercial aircraft production after members of its largest union voted overwhelmingly to down tools over a new three-year contract.

A work stoppage would be damaging for the company and force a further delay to the roll-out of the 787 Dreamliner, Boeing’s long-range jet that has been dogged by supply-chain problems and is already 14 months behind schedule after three separate delays to its production timetable.