 During the Second World War, Gran was reportedly a member of "Nasjonal Samling" (NS), Vidkun Quisling's collaborationist party.The NS used Gran's hero-like status in their war propaganda, and in 1944, a commemorative stamp was issued to mark the 30th anniversary of Gran's flight across the North Sea.It has been speculated Gran feared reprisals from the pro-German fascist party because of his commitment to the Royal Air Force in the First World War.