Around 18:00, Chinook ZD576 flew into a hillside in dense fog. The pilots were Flight Lieutenants Jonathan Tapper, 28, and Richard Cook, 30, both United Kingdom Special Forces pilots. There were two other crew. The helicopter was carrying 25 British intelligence experts from MI5, the Royal Ulster Constabulary and the British Army, from Aldergrove to attend a conference at Fort George (near Inverness) in Scotland. At the time of the accident Air Chief Marshal Sir William Wratten called it "the largest peacetime tragedy the RAF had suffered".