Swissport is set to cut more than half of its UK workforce as air companies struggle with the effects of the coronavirus crisis.
The firm said it was consulting on cutting up to 4,556 jobs.
Chief executive Jason Holt said the company had to reduce the size of its workforce to survive.
Swissport operates at airports across the UK, including Heathrow and Gatwick, which are among those badly hit by the crisis.
Air travel collapsed around the world after governments imposed travel restrictions during coronavirus lockdowns.
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While some airlines are making plans to start flying some routes again as lockdowns lift, Swissport has said its revenue is forecast to be almost 50% lower than last year due to the crisis.
Mr Holt said in a message to staff: "We must do this to secure the lifeline of funding from lenders and investors to protect as many jobs as possible in the UK and Ireland.
"It's true that we've seen tough times before - volcanic cloud, 9/11, the financial crisis - and we've weathered these. But this time it's different. We have never seen anything like Covid-19 in our lifetimes.
"We are now facing a long period of uncertainty and reduced flight numbers, along with significant changes taking place to the way people travel and the way goods move around the world.
"There is no escaping the fact that the industry is now smaller than it was, and it will remain so for some time to come."
Swissport employs about 8,500 workers at airports, including baggage handlers and check-in staff.
The GMB union said the announcement was "devastating news", with jobs set to be lost that were essential for regional economies.
Nadine Houghton, national officer of the GMB, said: "With Swissport now considering job cuts on this scale, we have deep concerns about the viability of many of our regional airports and the benefits for regional connectivity that they bring."
Oliver Richardson, national officer of Unite, said: "We can't wait any longer, the UK government needs to urgently intervene with a bespoke financial package and an extension of the 80% furlough scheme for the aviation industry."
The Unite union in Ireland confirmed that 287 workers at Belfast City Airport and Belfast International Airport face redundancy.
"This will be devastating news for these workers and their families. It is also entirely unnecessary - the government's Coronavirus Job Retention Scheme remains in place - these workers could continue to be furloughed. There is no need for any job-losses at this time. This is a disgraceful move solely rooted in the need to secure corporate profits," said George Brash, Unite Regional Officer for Swissport workers in Belfast.
"It is now absolutely imperative that we see urgent action in both Stormont and Westminster to safeguard our aviation sector, its workforce and the future of regional airports."
Staff at Swissport handle luggage after it's checked-in. They also de-ice and refuel planes and manage freight.
The company provides essential services for most UK airports and airlines.
Back in April Swissport UK warned it would have to slash thousands of jobs if more government support for the aviation sector was not forthcoming.
This latest announcement demonstrates how the deep the damage to the aviation sector is.
The pandemic has hit aviation hard and airlines and airports have already announced plans to scrap tens of thousands of jobs.
The Department for Transport has consistently said that while the aviation sector is important to the UK economy, all firms, including aviation companies, should first explore existing government schemes and try to raise capital from investors before the government will consider the situation of individual firms.
Industry association Airlines UK responded to Swissport's announcement by repeating its call for targeted government assistance for the sector.
"The need for a stimulus package of measures for the industry is now even more vital," said chief executive Tim Alderslade.
Next Monday, the government is expected to make an announcement on international travel corridors, which would allow people from the UK to visit selected countries without having to face a 14-day quarantine on their return.
Mr Alderslade welcomed that prospect, but added: "The government needs to do much, much more to help a sector very much on its knees."