Travel restrictions and a slump in demand due to the coronavirus have forced airlines to cancel most flights and temporarily reduce staff.
Virgin Atlantic will cut four-fifths of its flights and has asked staff to take eight weeks of unpaid leave.
Ryanair and EasyJet are grounding most of their fleets, while BA owner IAG is to cut capacity by 75%.
Norwegian Air has cancelled thousands of flights and will temporarily lay off more than 7,500 staff.
Holiday company Tui has said it will suspend the "majority" of its operations, affecting "package travel, cruises and hotel" bookings.
Passenger numbers and bookings have plummeted in recent weeks as countries closed their borders and holiday makers cancelled trips.
Virgin Atlantic said travel restrictions have "accelerated the sharp and continual drop in demand for flights".
The firm said that it was going to reduce its services to focus on "core routes". Its London Heathrow-Newark route will be cut immediately.
It added that it needed to reduce costs elsewhere. The airline will ask staff to take eight weeks' unpaid leave over the next three months, with the cost spread over six months' salary.
Virgin said it was doing this to avoid job losses, although it is also offering a voluntary redundancy package to all employees.
Norwegian Air's temporary reduction in staff numbers will affect pilots, cabin crew and maintenance workers, roughly equalling 90% of its workforce.
"There is no cash whatsoever coming in the doors," said aviation analyst John Strickland, who warned that airlines could lose money very quickly, despite such drastic measures.
