Birmingham Airport faces a pre-Christmas overtime ban or work to rule by workers in pursuit of their first pay rise in nearly four years.
Unite union members at the airport have rejected all-out strike action, but voted by 88 to 73 in favour of action short of a strike over a long-running pay dispute.
The airport was accused of misleading the public with a statement which revealed that only 70 workers had supported a strike and that the vote for a walkout had been defeated.
But Unite union regional official Peter Coulson said: “We have a clear mandate to take action short of a strike, which we intend to do.
“The airport claims that this will affect their passenger numbers but if that is what it takes to lever the door open for further negotiations, that is what I will do.
"Action short of a strike would mean a work to rule or an overtime ban, which could quite easily disrupt the airport.”
In a prepared statement, David Winstanley, Birmingham Airport’s Operations Director, said: “We are very pleased that union members have rejected strike action.
"We would like to apologise to our customers for any uncertainty and can reassure those flying through Birmingham Airport this Christmas that it is business as usual.”
But Mr Coulson said: “Birmingham Airport are misleading the general public. They have only put out half a story.”
Union representatives will meet next Tuesday to decide the next step. The union has 28 days before December 17 to take action.