Regional carrier Flybe has ceased trading and all scheduled flights have been cancelled.
The UK Civil Aviation Authority (CAA) made the announcement the company had gone into administration for the second time in three years, asking passengers booked on Flybe flights not to travel to airports.
It urged ticket-holders to instead check its website for the latest information.
CAA consumer director Paul Smith said: “It is always sad to see an airline enter administration and we know that Flybe’s decision to stop trading will be distressing for all of its employees and customers.
“We urge passengers planning to fly with this airline not to go to the airport as all Flybe flights are cancelled.”
The airline tweeted: “We are sad to announce that Flybe has been placed into administration.
“David Pike and Mike Pink of Interpath have been appointed administrators. Flybe has now ceased trading. All Flybe flights from and to the UK are cancelled and will not be rescheduled.”
Flybe was pushed into administration in March 2020 with the loss of 2,400 jobs as the Covid-19 pandemic destroyed large parts of the travel market, but returned to the skies in April.
Its plan was to operate up to 530 flights per week across 23 routes, serving airports such as Belfast City, Birmingham, East Midlands, Glasgow, Heathrow and Leeds Bradford, and it flew the most UK domestic routes between airports outside London.
Its business and assets were purchased in April 2021 by Thyme Opco, which is linked to US hedge fund Cyrus Capital, and Thyme Opco was renamed Flybe Limited and based at Birmingham Airport.
The Government said its priority was to support anyone trying to get home and those who have lost their jobs.
“This remains a challenging environment for airlines, both old and new, as they recover from the pandemic, and we understand the impact this will have on Flybe’s passengers and staff.
“Our immediate priority is to support people travelling home and employees who have lost their jobs,” a spokesperson said.
“The Civil Aviation Authority is providing advice to passengers to help them make their journeys as smoothly and affordably as possible.
“The majority of destinations served by Flybe are within the UK with alternative transport arrangements available.
“We recognise that this is an uncertain time for affected employees and their families.
“Jobcentre Plus, through its rapid response service, stands ready to support any employee affected.”
Freddie McBride, 61, from Balham, south London, branded Flybe “outrageous” after his flight from Heathrow to Belfast on Saturday morning was cancelled with just three hours’ notice, forcing he and his wife to rebook with Aer Lingus.
He told the PA news agency: “I got up at the crack of dawn, packed and we couldn’t check in online last night so I thought we’d do it this morning.
“I left my wife to do it while I got the train. I got up at six and left the house before seven. I got to Hatton Central and I checked my email and it says they’ve gone into administration. It’s just outrageous.
“I had to phone my wife to tell her and she booked from home while I was running about to terminal three and five to British Airways because I thought we could fly with them.”
He added: “When I get on the plane I’ll be relieved. They allowed us to book about a day or two ago. It’s not good, it’s not good.”
Labour called the news “devastating” as it urged the Government to act.
“Protection for passengers is simply not strong enough – and ministers have sat on their hands for years and failed to introduce long-promised airline insolvency laws,” shadow transport secretary Louise Haigh said.
“They must act, and urgently strengthen protections for passengers, employees and those affected,” she added.
Matthew Hall, chief executive of Belfast City Airport, said: “First and foremost, our thoughts are with Flybe employees and passengers affected by this disappointing and unexpected news.
“Passengers booked on Flybe flights should not travel to the airport and should seek further advice from the Civil Aviation Authority.”
Unite national officer for civil aviation Oliver Richardson said: “The Government has not learned the lessons from the original collapse of Flybe.
“It has failed to introduce the Airline Insolvency Bill, which would have allowed Flybe to continue to operate, avoided passengers being stranded and staff losing their jobs in the middle of the night.
“In recent years the UK has seen the collapse of Monarch, Thomas Cook and Flybe twice, how many more airlines will be allowed to plunge into administration before the Government introduces the measures needed to protect the UK’s aviation industry and its passengers?”