Roughly 600,000 travelers are stranded around the world after British travel provider Thomas Cook declared bankruptcy.

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• Thomas Cook, the storied British travel company and airline, declared bankruptcy early Monday morning, local time.
• About 600,000 travelers, including 150,000 Britons, were left stranded, leading the British government to begin the largest peacetime repatriation effort in history.
• The tour operator was still scrambling to secure an additional £200 million (roughly $249 million USD) in emergency funding on Sunday. The effort was apparently unsuccessful.
• Visit Business Insider's homepage for more stories.

Thomas Cook, a 178-year-old British travel company and airline, declared bankruptcy early Monday morning local time in the UK, suspending operations and leaving hundreds of thousands of British tourists stranded around the world.

The travel company operates its own airline, with a fleet of nearly 50 medium and long-range jets, and owned several smaller airlines, including German carrier Condor. The airline still had several flights in the air as of Sunday night, but was expected to cease operations once they landed at their destinations.

Around 600,000 Thomas Cook customers were reported to be traveling, of which were 150,000 British and were abroad, scheduled to fly home with Thomas Cook, according to reports.

The British Department for Transport and Civil Aviation Authority prepared plans, under the code name "Operation Matterhorn," to repatriate stranded passengers. However, travelers face delays of up to two weeks, according to the Telegraph.

The scale of the task has reports calling it the "largest peacetime repatriation effort" in British history.

Costs of the flights were expected to be covered by the ATOL - or Air Travel Organiser's License - protection scheme, a fund which provides for repatriation of British travelers if an airline ceases operations.

Airplanes from British Airways and easyJet would be among those transporting stranded passengers home, according to the Guardian, as well as chartered planes from leasing companies and other airlines. Thomas Cook Airlines' destinations included parts of mainland Europe, Africa, the US, the Caribbean, and the Middle East. Airplanes were being flown to those destinations on Sunday night, according to the BBC.

Read more: Singapore Airlines, one of the most ritzy airlines in the world, is partnering with a high-tech urban farm to make sure it serves the best meal on every flight. Take a look inside the futuristic operation.

The company was still selling tickets until Sunday night in the UK.

One Plymouth, England-based traveler, who had booked a holiday to the Greek island Zakynthos for August 2020, told Business Insider that she saw Thomas Cook had charged her more than £600 by direct debit on Sunday afternoon for the trip - she said that she was not due to be charged until September 26th. It was unclear whether she would be able to recoup the funds with the bankruptcy declaration.

On Sunday, the holiday company was left scrambling to secure £200 million - about $249 million - in emergency funding following a demand from its lenders. The company's executives were believed to have met Sunday with its biggest shareholder and creditors at a London law firm, according to Sky News and iTV.

Reports indicated that the tour operator failed to secure the needed funds during the meeting.

Although Thomas Cook had reached an agreement for a £900 million rescue deal, with Chinese company Fosun Tourism Group providing half of that funding, creditors had demanded the British company secure an additional £200 million.

Thomas Cook owns a Nordic operation, as well as airlines in the UK, Germany and northern Europe - proposals to fund those, while letting the UK tour operating arm fail, were deemed unfeasible, according to Sky News, as have several other options which would take too long to implement.

Thomas Cook, as well as a union representing some of its 9,000 UK employees, had sought an emergency funding plan from the British government. However, government sources "had questioned the financial wisdom of stepping in to save the company," according to the BBC. The company employs 21,000 globally.

The company had filed for Chapter 15 bankruptcy protection in the US last week, although it stopped short of declaring insolvency.

Although Thomas Cook had managed to recover from a risk of insolvency in 2011, it continued to be held back by lingering debts. It also suffered by lower demand over the past two summer travel season, as major heatwaves led many Britons to stay home. Brexit uncertainties and a weak pound also contributed, according to the Telegraph.