City of Derry Airport has said it has made improvements to its bird management system after its closure by the Civil Aviation Authority.
The regulator found fault with City of Derry Airport's safety provisions
It was shut on Friday by the CAA due to a "systematic failure of safety management".
Since then airport management and the CAA have been in talks on reopening it.
On Sunday, the airport said an agreed listing of remedial actions was under way along with an aerodrome audit and a review of the safety management system.
Contractors have also made improvements to the bird management system.
In a statement the airport described these as covering culverts and ponds with nets along with remedial repairs at various areas adjacent to the main runway.
City of Derry apologised for the uncertainty to passengers and said the closure was "an exceptional situation". A further update will be released later on Sunday.
Information lines have been set up and passengers are asked to call 028 71 305544 and 028 718 10784.
British Airways rescheduled their flights on Sunday to operate through Belfast International Airport.
British Airways Dublin and Glasgow services are affected and passengers should check-in as early as possible at City of Derry Airport for coach transfers to Belfast International.
Ryanair have cancelled all flights to and from the airport. Passengers may re-book from Knock or Dublin airports.
There is no word yet on when City of Derry will re-open.
Airport manager Seamus Devine said the closure followed a CAA audit of repair work at the site.
However, the authority said it had been in discussion with the airport "for some time" about safety issues.
These included no effective bird control plan and unsuitable temporary repairs to the area where planes park.
There was also poor runway drainage, said the authority.