Hundreds of thousands have been left stranded - but help is at hand.
ADVERTISEMENTThe collapse of Thomas Cook has left hundreds of thousands of people stranded abroad - and thousands more with the prospect of their upcoming holiday being cancelled.
There are some protections for consumers, which vary depending on the specific circumstances of the booking.
If you have purchased a package deal
If you have booked a package holiday from Thomas Cook, meaning a combination of a prearranged flight, hotel or car hire, you should be covered by the Package Travel Directive for bankruptcy.
Organisers of packages have to take out insolvency protection, which covers refunds and repatriation, as per EU regulations.
If you booked a package holiday with Thomas Cook, it is ATOL protected. The Civil Aviation Authority’s (CAA) website covers how to make an ATOL claim.
The CAA says it will have more information on refunds for those with ATOL protected bookings, on its website by 30 September.
Read more: Thomas Cook: Why did the world's oldest travel firm go bust?
If you are already on holiday
The government has launched Operation Matterhorn, the largest repatriation effort in the UK since the Second World War.
The government has said all passengers with a return flight to the UK within the next two weeks will be flown home, with the aim that this will happen as close to the time and date of the original flight as possible.
These repatriation flights are only for customers whose flight originated in the UK. The CAA has urged holidaymakers to check the status of their return flights on its Guidance by Destination page.
The repatriation flights will only be in effect for two weeks, so for any travellers with a flight later than 6 October, they will need to make their own alternative arrangements.
Simon Calder, the travel editor of the Independent website, told Euronews Operation Matterhorn means "UK travellers are in the strongest position" and are "really well looked after" as they may be flown back on the day they were expecting, so should continue to enjoy their holiday.
Read more: Largest peacetime repatriation effort begins after Thomas Cook collapse
If you have booked just a flight without ATOL protection
Those who don't have ATOL protection and are yet to fly, your flight is now cancelled, and you cannot make a claim through ATOL. In some cases, those who booked with a credit card may be entitled to claim money back - check with your credit card company.
Those with travel insurance should also check with their insurer as they may be due money back.
If you made a booking outside of the UK
The European Commission says it is "in contact with the National Enforcement Bodies in order to ensure passengers are informed about their possibilities to be re-routed or seek compensation".
It also says the EU set up the European Consumer Centres in each Member State, so passengers should consult their local centre for help and advice.