Passenger airliners, first Jets -
Even the Comet 1 series had 4, or sometimes 5 flight crew in the cockpit/pointy end, as did 707's & VC-10's on the Transatlantic & Pacific until NAV aids and Comms were much improved.
1. Captain
2. First Officer
3. Flight Engineer
4. Navigator/Second officer
5. Radio Operator
Plus, often would also carry a ground engineer as well for remote outstations.
Then we found ourselves in the late 1960's with old 80 seater DC-4's (such as Channel AW & Air Ferry) just flying around with 2 pilots.