 Johnson's wartime record was 515 sorties flown, 34 aircraft claimed destroyed with a further seven shared destroyed (three and one shared victories), three probable destroyed, 10 damaged, and one shared, destroyed on the ground. All his victories were fighters. As a Wing Leader, Johnson was able to use his initials "JE-J" in place of squadron code letters. He scored the bulk of his victories flying two Mk IXs: EN398 / JEJ in which he shot down 12 aircraft and shared five plus six and one shared damaged, while commanding the Kenley Wing; MK392 / JEJ, an L.F Mk. IX, 12 aircraft plus one shared, destroyed on the ground. His last victory of the war was scored in this aircraft. Johnson ended the war flying a Mk XIVE, MV268 / JEJ. His post-war mount was MV257 / JEJ; it was the last Spitfire to carry his initials.
