More than 2,000 holidaymakers are thought to have been affected by the collapse of Turkey specialist Exclusive Escapes.
The Surrey-based operator which had a turnover of around £10.8 million, went into administration yesterday.
It was also trading as Hidden Turkey, and had around 500 people abroad, the CAA said.
The association added that it had been in touch with hotels and airlines to ensure all their Atol protected holidaymakers were able to complete their holiday and return to the UK as scheduled.
Exclusive Escapes also had around 1,750 customers with forward bookings, the CAA said.
It added that Atol protected customers would be contacted in the coming days and informed that their holiday had been cancelled due to the company going into administration.
All forward bookings were Atol protected and customers will therefore get full refunds, the CAA said.
David Clover, head of crisis management at Atol said: “The collapse of Exclusive Escapes is a timely reminder of why holidaymakers should make sure their holiday is Atol protected and that they receive an Atol certificate, as soon as they’ve booked their trips.
“Sadly, booking an unprotected holiday could leave you out of pocket or stranded abroad if something goes wrong with your travel company.
“So if you are looking for a bargain air holiday at the end of summer sales , it is essential to check to make sure you will get an Atol protection and receive an Atol certificate before you hand over any money.”
The CAA has published advice for anyone affected by the collapse of Exclusive Escapes on its website and a claim form is on the CAA website.