A couple of years ago I was on a flight from Tulsa to Denver and I happened to be seated next to an engineer from Boeing Corporation (the airplane people). As I am interested in airplanes myself, I got to talking to him about the (then) new 777 aircraft that Boeing was producing. One issue of interest was the fact that the aircraft has only two engines and, as such, was subject to additional scrutiny by the FAA before it would be allowed to fly over large expanses of ocean.
As I queried the Boeing engineer on this issue of long flights over large bodies of water, he explained that Boeing was conducting what they called "ETOPS" testing, which (as I recall) stands for "Extended Twin-engine OPerationS." Or, as the Boeing engineers humorously refer to it: "Engines Turn Or People Swim."