Ryanair has confirmed it is to cut its morning flight from City of Derry Airport to London from October.
Ryanair is the biggest customer at the council-owned airport
The airline will operate only one evening flight a day from Londonderry to Stansted.
The move would appear to increase pressure on Derry City Council to push ahead with the controversial extension of the airport's runway.
Ryanair is the biggest customer at the council-owned airport.
However, for some time it has been making it clear it wants to see the runway extended to cope with the newer, larger aircraft it is bringing on-stream.
Now in publishing its winter timetable, the airline has said it has none of the older, smaller aircraft available to cover the morning flight.
As a result, it is being dropped.
The airline also warned that unless the situation was resolved by the spring, it would terminate all flights from the airport.
To complete the extension, the council is faced with the controversial and expensive prospect of buying and knocking down a number of homes.
The council said it remained committed to its development programme, and it was in the process of making final submissions to the secretary of state.