A major air and sea search was launched on Thursday evening when the light aircraft was reported overdue, and continued to 3am on Friday, when it was suspended due to fog.
The flight took off from the City of Derry airport and had been tracking towards Stranraer.
The UK Coastguard search and rescue helicopter based at Prestwick, and the Irish Coastguard helicopter based at Dublin, searched from the air, while Coastguard and RNLI lifeboats from Scotland and Northern Ireland were involved in the operation in the North Channel.
The search will resume once foggy conditions clear.
The Northern Ireland North West Mountain Rescue Team will join the search on Friday.
Ryan Gray, senior maritime operations officer at the UK Coastguard, said: “UK Coastguard has also issued a Mayday relay broadcast in the area and several merchant shipping vessels have responded and are keeping a lookout for this aircraft. We may send further resources as the search widens.”
The Police Service of Northern Ireland and Police Scotland have been informed.