A jet engine is a reaction-type engine that generates thrust by jet propulsion. Most jet engines are internal combustion engines that operate based on Newton’s third law. Broadly speaking, jet engines include rocket engines and air jet engines. Rocket engines have their fuel and oxidizer carried by the aircraft, including solid-fuel rocket engines and liquid-fuel rocket engines, and they are characterized by the ability to operate outside the atmosphere; air jet engines do not carry their own oxidizer but obtain air from the atmosphere as the oxidizer, including ramjet engines, pulse engines, turbojet engines, and turbofan engines, etc. The most commonly used air jet engine in modern air transport aircraft is the turbofan engine, which is characterized by high thrust, low noise, and low fuel consumption.