Asia travel specialist Gendai Travel has collapsed.
The London-based firm traded under the names Go Asia Travel, Japan Travel Centre, JTC Tours, PIC, and PIC UK.
The Civil Aviation Authority confirmed that the company ceased trading on Monday.
The CAA said: “We will contact consumers with Atol protected bookings directly.
“Please do not use claim forms from other failures as these cannot be accepted.
“We understand the company sold flight tickets under its Iata licence and as agent for the airline operating the flight.
“These flights are not Atol protected. Unprotected flights were typically those where full payment was made at the time of booking and a ticket was issued straightaway.
“Consumers should contact the airline shown on their tickets.
“Bookings which do not include a flight element are not covered by the Atol scheme and consumers should contact Abta.”