UK investigators believe two Cessna 208 turboprops were just 5 seconds from an almost certain mid-air collision on final approach, after each aircraft joined a landing circuit without visual contact with the other.

The collision was averted only by “the narrowest margin”, according to the UK Airprox Board, after the air-ground communication service operator realised the two aircraft were simultaneously descending towards the runway with one stacked above the other.

Neither pilot was aware of the other’s presence and the communication service operator ordered the higher aircraft to execute a go-around.