A turbojet is a type of an air-breathing jet engine. It consists of an inlet, compressor, combustion chamber, and turbine. Air from inlet is passed through the compressor where it is compressed, and then passed through the combustion chamber where it is heated. The flow is expanded through the turbine. Turbojets are highly efficient for supersonic aircraft. Turbojet engines were used in Concorde supersonic airplane, and other aircraft which fly supersonically. Turbojets are also used in cruise missiles. The efficiency of gas turbines can be increased by increasing the overall pressure ratio, higher-temperature compressor materials, and increasing the turbine entry temperature. A turbine engine has a smaller diameter which gives an advantage of size consideration. Turbojet engine has a lower specific weight that is the weight of the engine per unit of thrust produced.

Turbojet engine