Paramedics and three ambulance crews, plus two officers and an air ambulance were sent to the scene near Nutts Corner, County Antrim.
The Northern Ireland Ambulance Service said it received a call shortly after midday following reports of a downed aircraft. No patients were taken from the site of the crash.
A statement from Belfast International Airport said the aircraft was not operating to or from the airport.
Pat Catney, a Northern Ireland Assembly member, said: “My thoughts and prayers are with everyone involved in the ongoing incident at Nutts Corner following a crash.
“I understand that the Air Ambulance and the Northern Ireland Fire and Rescue Service are at the scene. I have been in touch with staff at Belfast International Airport and I will continue to monitor the situation closely.
“Thinking of all of those involved at this difficult time.”
A Police Service of Northern Ireland (PSNI) statement confirmed the two deaths.
The flight was not connected to either of the two Belfast airports or an airfield in Enniskillen, Co Fermanagh, spokespeople said.
Newtownards airport, where the Ulster Flying Club is based, said it would make no comment.
Additional reporting by agencies.