Monarch Airlines has ceased trading and all of its future bookings have been cancelled, the Civil Aviation Authority has said.
Around 110,000 customers are currently overseas and the government has asked the CAA to charter aircraft to bring them back to the UK.
Monarch is the UK’s fifth biggest airline and the country’s largest ever to go into administration.
Customers due to fly from the UK have been told not to go to the airport.
Monarch had been in last-ditch talks with the CAA about renewing its licence to sell package holidays.
It had until midnight on Sunday to reach a deal with the aviation authority but failed to do so.