“If the occupancy rate is good, you also increase fuel efficiency” is only true if all else is equal. In this case, it’s not: the hop from 2-engine to 4-engine

“If the occupancy rate is good, you also increase fuel efficiency” is only true if all else is equal. In this case, it’s not: the hop from 2-engine to 4-engine hurts fuel efficiency and adds to cost/complexity of the aircraft.