Britain's aviation regulator says tour operator K&S Holidays has gone bust.
It is the second British travel firm to go under this week. On Friday, tens of thousands of travelers were stranded when the country's third-largest tour operator XL Leisure Group collapsed.
Civil Aviation Authority (CAA) press officer James Hotson says K&S ceased trading Saturday.
However, he says 150 passengers overseas with the group can continue their vacations as normal because their flights will be covered by a bond.
Hotson says some 400 people with forward bookings will have their vacations canceled and receive full refunds.
XL Leisure Group went into administration Friday saying it had been unable to secure more funding.
The CAA, which took on the task of getting XL's passengers home, estimated there were 50,000 customers abroad who had booked through an XL tour operator, including 10,000 on holiday with XL Airways and 25,000 with other tour operators who shared the XL flights.
Some 200,000 customers had advance bookings with the XL tour operators, the CAA said.