Flybe customers have been warned "not travel to the airport" unless they have arranged new flights as a new bid for financial help to save the ailing airline failed.
It comes after the Exeter-based carrier managed to avoid going bust in January.
In a letter to airline staff, chief executive Mark Anderson said there was “no feasible solution” to keep trading.
Government officials say they will work closely with industry to minimise any disruption to routes operated by Flybe.
“Government staff will be on hand at UK airports ready to assist and we’re working with airline, train and bus operators to help people find alternative ways home," said Transport Secretary Grant Shapps on Twitter.
“We are also urgently working with industry to identify how key routes can be re-established by other airlines as soon as possible."
Some 2,000 jobs with the airline are now at risk.
In a statement, the UK Civil Aviation Authority said:" All Flybe flights, and those operated by Stobart Air, are cancelled. Therefore, please do not go to the airport as your flight will not be operating.
“For flights operated by Flybe franchise partners (Eastern Airways, and Blue Islands) passengers should make contact with that airline to confirm your travel arrangements.”
Dr Neil Robinson, a travel and tourism expert from the University of Salford Business School said the current situation was “not great” for the budget airline sector.
“The impact of coronavirus is the biggest immediate cause, with demand falling off a cliff, but the business has been in trouble for a while, with a recent bailout keeping it alive,” Robinson said.
“Customers wanting very low budget priced tickets and a highly competitive market has resulted in the company going out of business.
“In addition, one could argue that FlyBe had an identity issue that was hard to pin down, were they budget, small aviation service provider, regional airline host or did they have aspirations to be a key European airline.
“Those already in the budget sector, such as Easyjet and Ryanair, have the market cornered and others attempting to find a foothold in the market will find it hard. Interestingly a new order for 35 jets in 2010 has probably not helped things and might have resulted in extra capacity with few takers or new routes."
Ryanair’s Alejandra Ruiz said:” We are working with the CAA to accommodate passengers who may have been left stranded or have had their travel plans disrupted by the collapse of the airline.
“We again call for more robust and frequent stress tests on financially weak airlines and tour operators so customers are not the ones who suffer.”
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