As a long retired Qantas engineer I remember a story from when Qantas got their first Boeing 707-138. May be true, may be not. The then Chief Executive, Cedric ObanTurner [ accountant by profession] wanted to sack a lot of the engineers. His theory was 'that when I buy a new car it does not need major work until they had done 30,000 or 50.000 miles.' His logic was aircraft were the same and more engineers could be employed as the aircraft got older.