Twinjet

The first, common on large aircraft such as airliners, has a podded engine usually mounted beneath, or occasionally above or within, each wing.

The second has one engine mounted on each side of the rear fuselage, close to its empennage, used by many business jets, although some airliners like the Fokker 70, Douglas DC-9 and COMAC ARJ21 utilise such a design as well.

During that decade only McDonnell Douglas continued development of the trijet design with an update to the DC-10, the MD-11, which initially had a range advantage over its closest medium wide-body competitors which were twinjets, the in-production Boeing 767 and Airbus A300/A310.

Some modern commercial airplanes still use four engines (quad-jets) like the Airbus A380 and Boeing 747-8, which are classified as very large aircraft (over 400 seats in mixed-class configurations).

Early twinjets were not permitted by ETOPS restrictions to fly long-haul trans-oceanic routes, as it was thought that they were unsafe in the event of failure of one engine, so quad-jets were used.

Mostly, ETOPS certification involves maintenance and design requirements ensuring that a failure of one engine cannot make the other one fail also.

On a nonstop flight from America to Asia or Europe, the long-range aircraft usually follows a great circle route.

Hence, in case of an engine failure in a twinjet (like Boeing 777), the twin-jet could make emergency landings in fields in Canada, Alaska, eastern Russia, Greenland, Iceland, or the British Isles.

The Boeing 777 has also been approved by the Federal Aviation Administration for flights between North America and Hawaii, which is the world's longest[citation needed] regular airline route with no diversion airports along the way.