Baggage handlers at 17 airports including Heathrow and Gatwick have voted to strike in a dispute over pay, threatening chaos to summer flights.
No date has been set for the strike
Members of the TGWU employed by services group Aviance backed a strike in protest at a 2.5% pay rise offer.
The union said fresh talks would be held with Aviance management on Wednesday to try to avert stoppages.
It said members had voted for full industrial action but no dates had yet been set for strikes.
But any action which did take place would affect most major airports and airlines.
Amicus later said it was going to ballot hundreds of workers at Gatwick and Belfast airports for strike action in the same pay dispute.
The union is set to join talks with Aviance on Wednesday.
TGWU said it was now up to Aviance to "revisit" its 2.5% pay offer, which was rejected by the union earlier this year.
A spokeswoman for the union said the average wage for baggage handlers and check-in staff was between £15-16,000, and that 2.5 percent could not be considered a significant rise.
She added that the offer contrasted badly with last year's award of 4.2%, which was made at a time when the industry was facing tougher market conditions.
The aviation sector has seen an increase in passenger numbers since.
Union members voted 4-1 in favour of a strike.
TGWU national officer Brendan Gold said: "Everyone is aware that aviation is a tough market and nobody is better placed to know that than the baggage handlers and check-in staff.
"They also know that the volume of their work is increasing as the industry gets busier and passenger numbers break record levels.
"That being the case, they know a bad deal when they see one, which is why we urge Aviance to listen to their workforce and act to improve the deal on offer and so avoid a damaging dispute."
Members of the GMB union are being balloted to strike over the same dispute.
A spokesman for the Department of Transport said: "We hope that they resolve their differences quickly so that the travelling public will not be put to any inconvenience.
"But it's a matter for the two sides to negotiate."
Aviance, which is owned by the Go-Ahead group, employs more than 2,300 workers at Aberdeen, Belfast, Birmingham, Cardiff, Coventry, Edinburgh, Gatwick, Glasgow, Heathrow, Jersey, Leeds Bradford, Liverpool, Luton,
Manchester, Stansted, Southampton and Teesside airports.