Flights leaving Northern Ireland are returning to normal after the delays and cancellations of the last two days.
Backlogs in Northern Ireland airports are now being cleared
However, dense fog is continuing to cause problems for Christmas holiday travellers at Heathrow and other UK airports.
Hundreds of domestic flights and some international flights are grounded.
British Airways said it expected its services at Heathrow, Gatwick and London City airports to be affected well into the weekend.
Heathrow airport was worst affected on Thursday, but there were also problems at other airports.
However, the managers of George Best Belfast City Airport and City of Derry Airport said backlogs had gradually been cleared.
Brian Ambrose, of George Best airport, said the situation was now "looking very good".
"We have managed to get an additional aircraft in from Heathrow.
"We have a two-hour delay getting into Heathrow, with their traffic control slots, but with the additional flight, we are very hopeful that today, the entire backlog will be cleared.
Airports are advising anyone intending to travel to check the situation in advance.