- in the "old days", most of the time, the road to an airline jet cockpit was long. Prior to landing the big airline job most pilots flew in all manner of organisations over many years. You built up a reputation in the industry/military, people knew you, a trail if you like, a history - Chief Pilots etc could get the "gen" on you pretty quickly. A "good egg", "reliable", "a good pair of hands", etc etc.
That might have been true in the USA, it certainly wasn't in europe. Closest to the US might have been the UK, but even there BA had their flight school and nowadays their future pilot program, Lufthansa had their own flightschool since flying was allowed again after WWII in germany and only hired non-cadets if their demand was bigger than the supply of cadets.