On July 24, they left Barcelonnette-Saint-Pons Airfield in France heading for Italy.
The inquest heard that the weather conditions were good and the route had been well planned.
But the group took a wrong turn up the Maddalena Pass instead of the Larche Pass and whilst three of them managed to turn round, one had to make a forced landing.
The two-seater piloted by Mr Buck, who was a respected pilot but the least experienced of the party particularly over mountainous terrain, then turned back to check on the crashed plane.
But the manoeuvre went wrong and the craft stalled and spun into trees.