Originally Posted by
dixi188
I believe at the time all commercial aircraft in the USA, over 80,000 lbs max weight, had to have a flight engineer.
This is why the BAC 1-11 series 400 that American Airlines bought was certified at 80,000 lbs MTOW, and thus two crew, rather than the Identical 300 series which was 87,000 lbs MTOW.
The rules must have changed when the Boeing 737 and DC9 came along
The 737 was always above the FAA's 80,000lb limit so required three crew on the flight deck, which was one reason why it initially sold so poorly in the US with only United buying it. In the rest of the world it was always a two crew aircraft.