British tour operator Thomas Cook has ceased trading and all its hundreds of thousands of bookings canceled after the firm failed to secure rescue funding. The Civil Aviation Authority (CAA) announced the firm's collapse early Monday. More than 600,000 vacationers had booked through the company.

CAA said 150,000 are British customers now abroad who will have to be repatriated. They will be brought home "as close as possible" to their booked return date, according to a statement.

Flights will start operating Monday, with details of each flight to be posted on a dedicated website as soon as they are available. The emergency operation — codenamed Operation Matterhorn — will aim to bring home Britons currently on holiday with the firm, according to BBC News.

Peter Fankhauser, Thomas Cook's chief executive, said the collapse was a "matter of profound regret," BBC News reports. The group's four airlines will be grounded and its 21,000 employees in 16 countries — including 9,000 in the U.K. — will be left unemployed.

The debt-laden company had said Friday it was seeking 200 million pounds ($250 million) to avoid going bust, was in talks with shareholders and creditors to stave off failure.

Thomas Cook flies from Europe and the U.K. to tourist destinations around the world, including the U.S.

Most of Thomas Cook's British customers are protected by the government-run travel insurance program, which makes sure vacationers can get home if a British-based tour operator goes under while they are abroad.

Thomas Cook, which began in 1841 with a one-day train excursion in England and now operates in 16 countries, has been struggling over the past few years. It only recently raised 900 million pounds ($1.12 billion), including from leading Chinese shareholder Fosun.

In May, the company reported a debt burden of 1.25 billion pounds and cautioned that political uncertainty related to Britain's departure from the European Union had hurt demand for summer holiday travel. Heat waves over the past couple of summers in Europe have also led many people to stay at home, while higher fuel and hotel costs have weighed on the travel business.

The company's troubles were already affecting those traveling under the Thomas Cook banner.

Travelers affected

A British vacationer told BBC radio on Sunday that the Les Orangers beach resort in the Tunisian town of Hammamet, near Tunis, demanded that guests who were about to leave pay extra money for fear it wouldn't be paid what it is owed by Thomas Cook.

• CBS News