Britain's biggest ever peacetime repatriation has got under way in an effort to bring home 150,000 holidaymakers who were stranded after the collapse of Thomas Cook.
The move comes after travel giant Thomas Cook ceased trading in the early hours of Monday after failing to secure a last-ditch rescue deal.
Codenamed Operation Matterhorn, Richard Moriarty, chief executive of the CAA, said it had launched "what is effectively one of the UK's largest airlines" in order to repatriate British holidaymakers.
He said: "News of Thomas Cook's collapse is deeply saddening for the company's employees and customers, and we appreciate that more than 150,000 people currently abroad will be anxious about how they will now return to the UK.
Here's everything you need to know about the operation.
How will people be brought home?
Transport Secretary Grant Shapps said dozens of charter planes, from as far afield as Malaysia, have been hired to fly customers home and hundreds of people were working in call centres and at airports.
Mr Shapps said: "Thomas Cook's collapse is very sad news for staff and holidaymakers.
"The Government and UK CAA is working round the clock to help people.
"But the task is enormous, the biggest peacetime repatriation in UK history. So there are bound to be problems and delays.
"Please try to be understanding with the staff who are trying to assist in what is likely to be a very difficult time for them as well."
The operation is significantly larger than the one conducted after the collapse of Monarch Airlines two years ago.
When will stranded customers return home?
The Department for Transport (DfT) said all customers currently abroad with Thomas Cook who are booked to return to the UK over the next two weeks will be brought home as close as possible to their booked return date.
The CAA noted that repatriation flights are only available for passengers whose journey originated in the UK.
In the cases where some of Thomas Cook's package holiday bookings include flights with other airlines, your return flight will still be valid.
The repatriation programme only runs to Sunday 6 October.
Customers currently overseas should not travel to the airport until their flight back to the UK has been confirmed on the dedicated website thomascook.caa.co.uk.
Will customers have to pay for their flights home?
No. Thomas Cook package holiday customers will see the cost of their accommodation covered by the Government, through the Air Travel Trust Fund or Atol scheme, the DfT said.
When Monarch Airlines went bust in October 2017, the Government spent £60 million hiring planes to get passengers home. A figure has not been given but bringing back Thomas Cook passengers will likely cost more than this.
What is the ATOL scheme?
An Air Travel Organisers Licence (ATOL) protects you from losing your money or being stranded abroad. Travel firms selling air holiday packages must have an ATOL and must issue a certificate to you to prove that protection is in place.
If your tour operator were to fail, the CAA will make a refund to you, or, if you're abroad, it will arrange for you to finish your holiday and fly home.
What if the hotels are for more money?
If you are currently abroad on an ATOL protected package holiday, the Civil Aviation Authority will seek to guarantee your stay directly with your hotel.
The CAA notes that if your hotel is requesting payment from you, please call their call centre on +44 1753 330 330.
It advises you not to make a payment to your hotel unless instructed otherwise by the CAA team.
What if I am not ATOL protected?
ATOL protection generally only covers tourists who buy package deals. It also applies to some flight-only bookings, particularly when the tickets are not received immediately.
But if you bought a flight directly with an airline it is unlikely you will be covered.
Under normal circumstances, passengers who are not ATOL protected would be asked to find, and pay for, their own way home.
Thomas Cook Group, including the UK tour operator and airline, has ceased trading with immediate effect.— UK Civil Aviation Authority (@UK_CAA) September 23, 2019
All #ThomasCook bookings, including flights and holidays, have now been cancelled.
Holidaymakers can usually apply to their credit or debit card provider to be reimbursed. Not all travel insurance policies provide coverage when a firm collapses.
But in this case, the DfT said everyone on a Thomas Cook holiday with a return flight to the UK within the two weeks will be brought home free of charge, whether they are Atol protected or not and regardless of their nationality.
You probably wont be entitled to make a claim for out of pocket expenses and additional nights of hotel accommodation. But you may be able to claim from your travel insurer, bank or your credit card issuer.
What about future holidays?
All Thomas Cook holidays have been scrapped so if you have an upcoming Thomas Cook Airlines flight leaving from the UK, do not go to your UK airport.
Operation Matterhorn does not cover any outbound flights from the UK. And if you choose to book a new flight with another airline out of the UK, you will not be eligible for a repatriation flight.
You should be able to get a refund though. The CCA has details on how you can claim here.
What will happen to Thomas Cook shops and airlines?
Thomas Cook has around 600 stores on UK high streets which are expected to close. Thomas Cook Group employs around 21,000 people in 16 countries.
All flights have been cancelled, according to the CAA. Those based in the UK, Scandinavia and the Balearics carry the group's name, while their German sister company is named Condor.