Belfast City Airport has cancelled the majority of its flights amid a yellow weather warning for fog.
All of Wednesday's remaining departures, and all but two arrivals, have been cancelled.
The disruption is expected to continue until Thursday morning.
The alert, which was issued earlier on Wednesday, will be in place until 08:00 GMT.
"Due to adverse weather conditions across Northern Ireland, there may be some disruption to flights due to arrive and depart," the airport said.
The Met Office has said areas of fog will become more extensive throughout Wednesday evening, with visibilities in some areas falling below 100m (328ft).
Drivers have been warned of difficult driving conditions.
Freezing temperatures could also result in icy patches and freezing fog which is an additional hazard, the Met Office added.
Meanwhile, there have been calls for rural bus routes to be gritted after a minor incident involving a school bus in County Antrim on Wednesday morning.
More than 40 pupils from Cross and Passion College in Ballycastle were on board when their bus slid on black ice on the Coolkeeran Road near Armoy and hit a wall.
It is the third incident in Northern Ireland involving a school bus in six weeks.
The school's assistant principal Ciaran McMullan said no pupils were injured in the incident, but said there are lessons to be learned from the "near miss".
Mr McMullan added it was clear the bus driver knew the small road well which helped avoid a major incident.
"As I understand, the bus very slowly glided or drifted towards the wall that it did eventually hit and thankfully nobody was hurt or injured or traumatised," he said.
"But it was, what I would describe as, a near miss."
The Department for Infrastructure (DfI), which is responsible for gritting the roads, said it salts the main through routes which carry more than 1,500 vehicles a day - meaning that 28% of the road network will be salted.
"In exceptional circumstances, roads with difficult topography carrying between 1,000 and 1,500 vehicles daily will also be salted," a statement added.
But North Antrim assembly member (MLA) Philip McGuigan said there should be some flexibility in this criteria.
Translink said a bus carrying schoolchildren to Cross and Passion School made "minor contact with a wall amid icy conditions" on Wednesday morning.
“Translink engineers salted the road and the bus was checked and able to continue its journey. There were no injuries reported.”
Elsewhere, in the Republic of Ireland, Met Éireann has also issued a yellow alert for fog for 17 counties, including Cavan, Donegal, Dublin, Galway, Kildare, Laois, Leitrim, Longford, Louth, Mayo, Meath, Monaghan, Offaly, Roscommon, Sligo, Westmeath and Wicklow.
It will be in place until 06:00 local time on Thursday.