Complex sentence: Owing to a shortage of Fleet Air Arm pilots in the 1950s, four supply officers qualified as fixed-wing pilots; both Brian Brown and Andrew Richmond rose to flag rank in the 1980s.
Split into simpler sentences: Owing to a shortage of Fleet Air Arm pilots in the 1950s, four supply officers qualified as fixed-wing pilots. Both Brian Brown and Andrew Richmond rose to flag rank in the 1980s.