Strike action could hit Glasgow and Edinburgh airports this summer after 600 Menzies Aviation ground staff rejected pay offers.
Workers in roles including dispatchers, allocators, airside agents and controllers at both airports turned down pay rises of around 4% to 4.25%.
At Glasgow airport, around 300 workers rejected a 4.25% offer.
At Edinburgh airport, about 300 workers turned down a similar 4% increase, with 100% voting against it.
Sharon Graham, general secretary at Unite, said: “Unite’s Menzies members have emphatically rejected unacceptable pay offers.
“The Menzies group is posting sky-high profits and our members who contribute towards this success deserve far better from the company.”
Carrie Binnie, industrial officer at Unite, said: “Summer strike action looms over Edinburgh and Glasgow airports because the pay offers on the table from Menzies Aviation aren’t good enough.
“Menzies Aviation has the ability to improve its offers and they can easily resolve this pay dispute without any disruption to the travelling public.
“If the company fail to table a better offer to our members, Unite will have no option but to ballot our members for strikes over the summer holidays.”
Phil Lloyd, senior vice president UK, Menzies Aviation, said: “Following the rejection of recent pay award proposals, we remain committed to seeking a resolution.
“We have invited Unite to return to the table to continue discussions this week and hope to reach an agreement which is workable for both the business and our employees at both Edinburgh and Glasgow.
“We will continue to work to pursue an agreeable solution to protect services for our airline and airport partners and their customers.”