Stobart Air has ceased trading and is in the process of appointing a liquidator.
The regional carrier had operated a number of short-haul flights on behalf of Aer Lingus.
The Dublin-based airline connected a range of UK airports with points in Ireland across 12 routes.
All have now been cancelled.
A statement from Aer Lingus said the company has been informed that Stobart was terminating its franchise agreement with the airline.
“As a result, all Aer Lingus Regional flights operated by Stobart Air are cancelled,” the airline said.
“Customers who were booked to travel on flights operated by Stobart Air are advised not come to the airport and to check the Aer Lingus website for updated information on refund or re-booking options.”
The statement added: “Stobart Air referred to the continuing impact of the pandemic which has resulted in almost no flying since March 2020.
“Stobart Air has ceased trading and is now in the process of appointing a liquidator.
“Aer Lingus apologises to customers for the inconvenience caused by the cancellation at such short notice of all flights operated by Stobart Air.
“Aer Lingus is now communicating to customers to advise them of their options for refund or re-booking.”
Around 480 jobs are expected to go following the collapse.
Commenting on the news Rory Boland, Which? Travel editor, said: “Aer Lingus passengers who have been affected by these cancellations will want to know that their money and bookings are safe, so it is right that the carrier is contacting passengers to discuss their refund or rebooking options.
“It must also ensure that any passengers left stranded as a result are rebooked onto an alternative flight at their earliest convenience.
“Stobart Air ceasing trading will be sobering news for the industry as the pandemic’s impact continues to wreak havoc on the travel sector.
“With most foreign travel still grounded, it’s vital the government steps in with tailored support for the travel industry.”