Some holidaymakers affected by airline Flyglobespan's collapse will be able to claim a full refund - but it depends on how they booked their trip.
Those who paid by credit card or used a tour operator affiliated to the Air Travel Organisers' Licensing (Atol) scheme should get their money back.
But people who used a debit card to book directly with Flyglobespan might not be protected.
A statement posted on Flyglobespan's website by the company's administrators said customers who booked a package holiday through The Globespan Group plc were likely to be protected.
But those who booked flights through Globespan Airways Limited, operating as Flyglobespan, are unlikely to be covered by the Atol scheme, the administrators PricewaterhouseCoopers said.
People who booked with The Globespan Group plc should be able to stay in their hotel or villa and complete their holiday.
In the majority of cases, the Civil Aviation Authority (CAA) will pick up the bill. It will also arrange for people to be flown home, the administrators said.
But those who booked directly with Flyglobespan will have to pay again for their return flight.
Passengers can make a claim for their expenses through the stricken company's administrators - but there is no guarantee this will be successful.
The administrators said Flyglobespan passengers already abroad would need to make their own arrangements to return to the UK using alternative airlines - and advised them to look out for special "repatriation" rates.
The administrators added that passengers may be covered by their travel insurance, credit card or Visa debit card.
Rochelle Turner, from Which? Holiday, said: "This has been a disastrous week for anyone planning to fly this Christmas.
"With yet another airline collapsing leaving thousands of Brits stranded either overseas or with future flights that they cannot take, it's really important that people take steps to ensure they are protected should a similar incident occur in the future.
"If you pay for your flight with a credit card, Visa debit card or book it as part of a package holiday, then you shouldn't have any problems getting your money back.
"The same applies for people who book through an Atol-bonded travel agent or operator.
"You may even be covered by your travel insurance as some policies cover scheduled flights.
"Sadly, if these don't apply to you, there's little hope of you seeing your money again so bear this in mind when you book your next flight or renew your travel policy."