The man, who has not been named, was taken to the Royal Lancaster Infirmary after the crash at Great Knoutberry Hill, near Dent, on Saturday afternoon.
A passenger in the aircraft was also treated for injuries said not to be life threatening.
Cumbria Police said the crash had been referred to the Air Accidents Investigation Branch.
At 2,205ft (672m), Great Knoutberry Hill, also known as Widdale Fell, straddles the border between Cumbria and Yorkshire.
A gyrocopter pilot was airlifted to hospital after his aircraft crashed on the summit of a Lake District mountain.