Virgin Atlantic has announced it is to cut more than 3,000 jobs in the UK and end its operation at Gatwick airport.
The shock announcement comes after rival British Airways said it could not rule out closing its Gatwick operation. Pilots' union Balpa described it as "devastating".
Many airlines have been struggling as the coronavirus pandemic has brought global travel to a virtual standstill.
The airline currently employs a total of about 10,000 people.
Virgin Atlantic, which is in the process of applying for emergency loans from the government, said that jobs will be lost across the board.
"We have weathered many storms since our first flight 36 years ago but none has been as devastating as Covid-19 and the associated loss of life and livelihood for so many," said Virgin Atlantic chief executive Shai Weiss.
Balpa the union said: "This is another terrible blow for the industry and is evidence of the dire situation facing UK aviation.
Balpa general secretary, Brian Strutton, said: "Our members and all staff in Virgin Atlantic will be shocked by the scale of this bombshell. We will be challenging Virgin very hard to justify this."
Virgin Atlantic also said it will move its flying programme from Gatwick to Heathrow. It said it intended to keep its slots at Gatwick "so it can return in line with customer demand".
However, Mr Weiss said there was no certainty when the air travel industry would recover from the coronavirus crisis.
"After 9/11 and the global financial crisis, we took similar painful measures but fortunately many members of our team were back flying with us within a couple of years.
"Depending on how long the pandemic lasts and the period of time our planes are grounded for, hopefully the same will happen this time."
Gatwick said the company was "very saddened" to hear of Virgin Atlantic's plans.
The airline has flown from the airport since 1984, and Gatwick said: "Virgin Atlantic will always be welcome at Gatwick and we will continue our efforts to explore ways to restart the airline's operations as soon as possible, in the knowledge that they intend to retain their slot portfolio at Gatwick for when demand returns."
Tim Alderslade, chief executive of aviation industry group Airlines UK, said: "The challenges facing UK aviation cannot be overstated. There is currently close to zero passenger demand and many airlines have ceased operations altogether.
"We do not know when countries will start to reopen their borders, or whether restrictions will remain in place for some time.
"Airlines are having to adapt to a sector that will be smaller and leaner in future, with no guarantees as to when we will return to pre-crisis levels."
It was 28% at British Airways. Now 30% of jobs will be lost at Virgin Atlantic.
The UK's aviation sector is shrinking in size. No airline or airport is immune.
Virgin Atlantic was Gatwick's ninth-largest airline, so it's a blow, but not a knock-out punch.
However, British Airways, which is Gatwick's second-biggest customer, has indicated that it also might not restart its Gatwick operation.
If BA does pull out, it would carry deeper ramifications.
Just a few weeks ago, several UK airports had elaborate, expensive and very controversial expansion plans in the pipeline. The big ones were operating at or very near capacity.
But the whole aviation sector is living a new reality.
When lockdown restrictions ease and flight schedules are increased again, there will be fewer passengers, fewer and probably more expensive flights and sadly thousands of cabin crew, pilots and ground staff will have lost their jobs.
And the consensus is that it will take years for the aviation sector to bounce back to where it was before the pandemic.
Commenting on its own future, Gatwick said: "We remain very optimistic about the long-term prospects of Gatwick Airport and our resilience as a business, and having remained open throughout this pandemic we are in a strong position to extend our current operations quickly to meet demand."
Other airlines have already announced that they intend to cut jobs because of the collapse in demand for travel due to the coronavirus pandemic.
Last week, British Airways said it was set to cut up to 12,000 jobs from its 42,000-strong workforce. It also told staff that its Gatwick airport operation might not reopen after the pandemic passes.
Ryanair has also said it will cut 3,000 jobs - 15% of its workforce - with boss Michael O'Leary saying the move was "the minimum that we need just to survive the next 12 months".
Virgin Atlantic said it had begun a 45-day consultation period on the job losses with unions Balpa and Unite.
Virgin Atlantic also plans to reduce the size of its fleet of aircraft from 45 to 35 by the summer of 2022.
It hopes to restore about 60% of its pre-pandemic flying capacity by the end of 2020.
Meanwhile, the airline industry has said it must be ready with a series of measures to prevent the spread of coronavirus before air travel can resume.
The International Air Transport Association (IATA) said it recommended mandatory face-coverings for passengers and masks for crew, as one of several actions to reduce what it called "the already low risk of contracting Covid-19 on board aircraft".
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