Aircraft Wiki

The trijet is an aircraft engine configuration where the plane features three jet engines (one of them generally placed in the tail), this category is mostly seen on airliners though there isn't currently any in production anymore due to twin jet popularity and lower operation costs.


  • S-duct

It's the most common trijet configuration known, in this case the air intake is under the vertical fin which catches



the air and then it descends to an inclined duct to the center body level until it finally meets the engine and scapes through the center-back of the plane. It's name comes from the letter "S" shape of the duct. The Boeing 727 and Lockheed L-1011 Tristar feature this system.

  • Direct flow

It's a more simple configuration where a unique structure holds the air intake and the engine generating a lineal flow that comes in and comes out in a straight line. The McDonnell Douglas DC-10 and MD-11 are the only aircraft with this variant.


Commercial Airplanes[]

MD-11 Fedex

Mcdonell Douglas MD-11 of Fedex Express

Business jets[]

Military aircraft[]

  • Martin XB-51