NPCwithnopurpose t1_izfk6at wrote

From a quick google search, a 747 can’t really maintain altitude with one engine, unlike twin jets. So, 50% of engines to maintain altitude in either case, but the 747 will cost more. That said, one engine providing thrust (to exclude APUs) is better than none. Also, the loss of an engine will probably just lead to an early landing anyway. The pilot just has more options when they started with 4 engines