The airlines decided to ask for a trijet, which is a plane with three engines.

A trijet is an aircraft powered by three jet engines.

The MD-11 was the most advanced trijet aircraft to be developed.

In 1964 this rule was lifted for trijet designs, as they had a greater safety margin.

The S-duct was easier to service than alternative trijet designs.

Boeing also said that they would make a Boeing 747 trijet.

At the same time, the manufacturer was searching to reduce wing and engine drag on the trijet.

This led to a flurry of trijet designs, which by 1980 had become the most popular airliner configuration.

The plane is a modernized version of the DC-10, which also features the trijet configuration.

Eventually the airlines agreed on a trijet.

The decision by both companies to build a trijet meant that the market was open for a smaller twin from Europe, the Airbus.

A twinjet design is more fuel-efficient than a comparable trijet or four-engined aircraft.

However, talks terminated as McDonnell insisted on the continuation of its trijet heritage.

Airbus filed a patent in 2009 for a new, twin-tail trijet design, but it is unknown if this will ever be developed or produced.

Thus, the Board of Directors decided in November 1983 to cease once more all work on the projected new trijet.

The 727 is Boeing's only trijet aircraft, as well as the only one without a conventional tail.

The plane, which first went into production in 1988 is the world's only large wide-cabin trijet, with engines mounted on the tail and under each wing.

Today, both narrow-body and wide-body trijet production has ceased for almost all commercial aircraft, being replaced by twinjets.

An S-duct is a type of jet engine intake duct, used in several types of trijet aircraft.

Under the previous method, McDonnell Douglas expected to spread out the trijet's costs until the company delivered 301 planes.

Dan-Air was the first British operator of the Boeing trijet, at the time the world's best-selling commercial jetliner.

Airbus twin-tail trijet, status unknown.

The plane is the first new trijet introduced since the Douglas DC-10 and Lockheed L-1011 two decades ago.

It was developed for Aeroflot as a replacement for the medium-range Tupolev Tu-154 trijet.

Dassault Falcon 50 Trijet.