The airlift to repatriate as many as 85,000 XL travellers stranded around the world, from Turkey to Barbados, will be the largest such effort for 20 years and could take at least two weeks, it emerged last night.

Richard Taylor, a spokesman for the Civil Aviation Authority, said it would involve chartering dozens of aircraft and was likely to cost at least £20 million.

Phil Wyatt, XL's chief executive, said he had talked to the CAA about the possibility of XL planes being used to bring stranded tourists back to Britain. “Unfortunately it's been deemed by the authorities - the Government, whoever - that that's impossible. I personally don't believe that's the case,” he said.

He said there were tens of thousands of people “who could have flown back on XL Airways that are going to come back on God-knows-what carriers that the CAA find. It's going to be the most challenging airlift, I believe, that anyone has undertaken.”

The CAA said that officials were drawing up lists of stranded travellers and had begun booking aircraft from rival operators, including Thomsonfly, Thomas Cook, MyTravel and BA. The first of these left London Heathrow yesterday at 6.30am for Mahon in Minorca. The Airbus A320 was operated by BMI, which said it had provided a back-up aircraft and crews available around the clock to assist with rescue flights for the next two weeks. Others, including Ryanair and flybe, also said they had offered aircraft.

Mr Taylor said that passengers would be contacted by other tour operators with representatives on the ground at resorts around the world and informed of travel arrangements.

David Clover, a spokesman for the Air Travel Organisers' Licensing (ATOL) scheme, which checks tour operators and travel groups, said the collapse of XL was a “huge failure” and called on holidaymakers to be patient. If they preferred to make their own way home, they could submit a claim for additional costs afterwards.

The CAA estimated that there were 50,000 tour operator customers of XL UK abroad, plus a further 10,000 who flew with XL Airways and 25,000 with other tour operators who shared XL's flights. While most of the stranded XL travellers who had booked their holidays with registered agents will be insured under the ATOL scheme, a special insurance programme administered by the CAA, others will have to foot the bill themselves if they booked directly through XL.com.

The collapse of XL Leisure, the UK's third-largest package tour operator, represents the largest failure of its kind since 1991, when Intersun plunged into bankruptcy.

The cost of the programme will be covered by the ATOL scheme. Since April, ATOL package-tour operators have contributed £1 from every ticket sold into a fund to cover such situations.

Virgin Atlantic said that it would offer discounted flights home from passengers stranded in Florida. “Our priority is to help passengers who are overseas over the next two to three weeks,” a spokesman said. “We have already seen hundreds of people turning up to our ticket desks and ringing us.”

Peter Long, chief executive of TUI Travel, one of XL's biggest competitors, said the group would be helping customers in Egypt and the Mediterranean.

Passengers may also be protected by some forms of travel insurance, and payment by Visa debit card may offer protection. However, people who booked a flight directly with XL Airways and paid with another kind of debit card will not be protected. They will have to pay again to get a flight home. They can make a claim for their expenses through the company's administrators, Kroll, but there is no guarantee of success.

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