Obviously over vast oceans it's critically important for airliner engines to be reliable and powerful. But hey, it's a business, so the engines also have to be efficient enough to keep airline fuel costs low. Decades ago, that meant ultra long haul were likely four-engine planes, like the 747. In the unlikely event that an engine failed, the other three engines could power the plane the rest of the trip, no problem. The downside: Four engines guzzle a lot of fuel.