Complex sentence: The new company had inherited a mix of aircraft from its predecessors, it quickly retired the Standard VC10s it had inherited from BOAC and the last Vickers Vanguards that came from BEA.
Split into simpler sentences: The new company had inherited a mix of aircraft from its predecessors. It quickly retired the Standard VC10s that had come from BOAC and the last Vickers Vanguards from BEA.