My old pilot served in three air forces. He was under training in the Polish Air Force when Germany invaded in 1939 and escaped via Hungary to France, where they joined the French Air Force. He was sent to continue his training to North Africa and when France adopted the Vichy regime these left for England to join the RAF. He eventually signed on to age 55 and would have left the RAF in the mid 1970’s, although he continued in a civilian role for some time after wards.