City of Derry Airport was closed yesterday due to a "systematic failure of safety management," the UK's Civil Aviation Authority has said.
The authority said the provisional suspension, which took effect from midnight on Thursday, followed safety concerns which arose following an inspection of the airport.
To suspend the licence of an aerodrome operating commercial flights was "fairly unprecedented" and had not been done for at least 15 to 20 years, a spokesman for the authority said.
The airport was given an opportunity to offer "robust and compelling solutions" to the problems pointed out by the authority.
The problems centred on drainage of the runway, the facility for parking planes and its bird plan. Once satisfied, however, this would be done, reinstating a full licence was "fairly straightforward", the authority spokesman said.
The "worst-case scenario" for the airport, which carries about 20 scheduled flights to Glasgow and Bristol every day and additional chartered flights to sun destinations in the summer, would be to have its licence revoked, the spokesman said.
Talks took place yesterday in London between management of the airport, owned by Derry City Council, and the Civil Aviation Authority.
Ryanair, which operates a service between Derry and London Stansted, cancelled its flight and promised a full refund to thwarted passengers.
Passengers on British Airways flights to Dublin and Glasgow Prestwick checked in as normal before boarding buses for Belfast International, about 70 miles away, where the flights have been rescheduled.
A spokesperson for the airport said passengers were taking the change of plans in their stride. "It's not been too bad and people have been goodwilled."
The spokesperson insisted safety was placed as a top priority and management said it was working to resolve the situation as quickly as possible.
The airport spokesperson added: "While this is an exceptional step by the CAA, the airport is confident that a position can be reached to ensure the airport is operational as soon as possible."