Regional airline Flybe has cancelled dozens of flights this morning, blaming "shortages of pilots" and "Easter holidays", among other "operational reasons".
Ten flights in and out of Belfast and four from Birmingham have been cancelled. Departures from Edinburgh, Newcastle, Southampton, Leeds Bradford and Aberdeen have also been called off.
The airline said it would like to "sincerely apologise for any inconvenience caused".
"All customers affected have been emailed and advised they can rebook for travel on an alternative flight or apply for a full refund," the company said in a statement.
The company has recently moved to a summer timetable however it will not confirm whether this has contributed to the cancellations.
What to do if your flight is cancelled
Flybe’s company statement said, "We have already identified several mitigation actions and will be issuing further updates throughout the day.
"All those affected have been emailed and advised they can re-book for travel on an alternative flight or apply for a full refund."
Flybe's website says that any customers who are at the airport when they find out their flight is cancelled should go to the Flybe customer services desk.
Those who have not arrived at the airport can contact the customer services desk. The UK number is 0371 700 2000. Those outside the UK can call +44 (0)207 308 0812.
On Monday passengers who were supposed to fly on a new route from Newquay to Heathrow were faced with a six-hour replacement coach service after their flight was grounded.