Back in the War, there were a number of 'elderly' aircrew who'd flown in the previous conflict.
Group Captain Stanley Vincent was the only RFC/RAF pilot to shoot down enemy aircraft in both world wars. Vincent was station commander of RAF Northolt during the Battle of Britain (aged 43), and claimed seven unconfirmed kills. After the war he became the 'father' of the BBMF.
Colonel Marcel Émile Haegelen was a World War I French flying ace credited with 22 victories in the Great War. Mobilised as fighter pilot at the beginning of World War II, he gained his 23rd victory on 14 June 1940 while flying a Curtiss H 75.
Theodor "Theo" Osterkamp was a German fighter ace scoring 32 victories in World War I. He led Jagdgeschwader 51 through the Battle of Britain (until replaced by Werner Mölders on 23 July) and claimed a further 6 victories. He was 48 years old during the Battle.
Oberst Harry von Bülow-Bothkamp scored six victories in World War I, he became a Luftwaffe ace in World War II, leading Commodore of Jagdgeschwader 2 and scoring 12 additional victories. He was 43 years old during the Battle.
Oberstleutnant Erich Mix trained as a fighter pilot and posted to Jagdstaffel 54, where, as an Unteroffizer from June 1918 until the end of the war, he scored three aerial victories (and one unconfirmed balloon). He commanded III./JG 2 in March 1940 and claimed eight (potentially 13) aerial victories before becoming one of the older, WWI era commanders dismissed by Göring in favour of younger, up-and-coming aces in September 1940.