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

The CAA said the cancellations left about 150,000 British customers abroad and in need of repatriation. They will be brought home "as close as possible" to their booked return date, according to a statement.

"Rescue" flights, run by a number of other airlines and chartered by the CAA at British tax payers' expense, were to begin operating Monday to get Britons back home. The government's emergency operation — code named Operation Matterhorn — will aim to bring home Britons currently on holiday with the firm, according to BBC News, which said the first wave of repatriations would be for about 16,000 people who were scheduled to fly with Thomas Cook back to the U.K. on Monday.

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The CAA said it hoped at least 14,000 of them would be put on chartered flights to come home more or less as scheduled.

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

The debt-laden company had said Friday it was seeking 200 million pounds ($250 million) to avoid going bust, and was in talks with shareholders and creditors to stave off failure. By Monday morning those efforts had failed and the firm was going into forced liquidation.

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

Thomas Cook aircraft await departure on the runway at Terminal 1 at Manchester Airport on September 22, 2019, in Manchester, England. Getty

Most of Thomas Cook's British customers are protected by the government-run travel insurance program, which puts the CAA in charge of getting vacationers home if a British-based tour operator goes under while they're 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.

Passengers wait to go through to the Thomas Cook check-in desks at Manchester Airport on September 22, 2019, in Manchester, England. Getty

Travelers affected

Several British vacationers told U.K. news outlets over the weekend that the Les Orangers beach resort in the Tunisian town of Hammamet, near Tunis, had demanded that guests who were about to leave pay extra money, for fear it wouldn't be paid what it was owed by Thomas Cook.

Ryan Farmer, of Leicestershire, told the BBC that many tourists refused the demand, since they had already paid Thomas Cook, so security guards shut the hotel's gates and "were not allowing anyone to leave."

It was like "being held hostage," said Farmer, who was due to leave Tuesday. He said he would also refuse to pay if the hotel asked him.

By Sunday, after apparent intervention by the British embassy in Tunisia, the standoff appeared to have been resolved and the resort said guests were free to leave. It was unclear whether the British government had reached an agreement with Les Orangers to ensure the resort received the payments it was due for all Thomas Cook-booked visitors, or whether the hotel might try to intervene with guests scheduled to leave in the coming days.

Kris Van Cleave contributed to this report.