About 110,000 customers are currently overseas and the British government has asked the CAA to charter more than 30 planes to bring them back to the UK.
This process is the UK’s “biggest ever peacetime repatriation”, Transport Secretary Chris Grayling said.
Monarch; which employs about 2,100 people, reported a £291m loss last year.
The airline – the UK’s fifth biggest and the country’s largest ever to collapse – was placed in administration – at a time when there were no Monarch planes in the air.
Passengers; many of whom were already at airports, were then sent text messages informing them flights had been cancelled.
In all, the 300,000 cancellations could affect up to 750,000 people.