Thousands of holidaymakers could face disruption if union members at BAA airports vote in favour of strike action.
Results are expected this afternoon of a ballot involving ground staff, firefighters and security staff.
The airports involved are Heathrow, Stansted, Glasgow, Edinburgh, Aberdeen and Southampton.
The dispute is over pay, with the union calling BAA’s offer of a 1% increase “paltry”.
It is expected that 300,000 holidaymakers would be affected by a walk-out, which could take place as soon as August 19. However it is thought the August bank holiday could be a target date.