U.K.'s Civil Aviation Authority (CAA) said on Monday Britain's Monarch Airlines ceased operations with immediate effect, leaving 110,000 customers stranded overseas and about 300,000 future bookings cancelled.
"We're sorry to announce that Monarch has suspended flights and holidays," Monarch said on Twitter.
"This is the U.K.'s largest ever airline to enter administration," CAA said.
The government has asked CAA to charter more than 30 aircraft to bring back to the U.K. Monarch Airlines customers currently overseas, CAA said in a statement.
The government has begun the biggest ever peacetime repatriation effort to return the affected passengers, Department for Transport, Foreign and Commonwealth Office said in a statement.
Monarch said on Thursday it was talking to potential partners after a report that parts of its short-haul network would be sold.