LONDON (AP) — British tour company Thomas Cook collapsed early today after failing to secure emergency funding, leaving tens of thousands of vacationers stranded abroad.

The British government said the return of the 178-year-old firm’s 150,000 British customers now in vacation spots across the globe would be the largest repatriation in its peacetime history. The process began today and officials warned that delays are inevitable.

The Civil Aviation Authority said Thomas Cook has ceased trading, its four airlines will be grounded, and its 21,000 employees in 16 countries, including 9,000 in the U.K., will lose their jobs. The company several months ago had blamed a slowdown in bookings because of Brexit uncertainty for contributing to its crushing debt burden.

The company had said Friday it was seeking 200 million pounds ($250 million) to avoid going bust and was in weekend talks with shareholders and creditors to stave off failure. The firm, whose airliners were a familiar sight in many parts of the world, also operated around 600 U.K. travel stores.

The company’s chief executive, Peter Fankhauser, said in a statement read outside the company’s offices Monday morning that he deeply regrets the shutdown.

“Despite huge efforts over a number of months and further intense negotiations in recent days we have not been able to secure a deal to save our business,” he said. “I know that this outcome will be devastating to many people and will cause a lot of anxiety, stress and disruption.”