Complex sentence: In early 1939,1 and 2 Transvaal Air Squadrons were formed These were training units based at Waterkloof Air Station comprising 18 aircraft, divided into 3 flights each, plus a headquarters or administrative flight per squadron.
Split into simpler sentences: In early 1939,1 and 2 Transvaal Air Squadrons were formed as training units based at Waterkloof Air Station. Each squadron comprised 18 aircraft, divided into 3 flights each, plus a headquarters or administrative flight per squadron.