A jet, also known as a jet aircraft or jet plane, is a fixed-wing aircraft that is powered by jet engines. Jet planes are the most efficient at speeds that are close to or above the speed of sound. The first jet plane, Heinkel He 178, was developed by Hans von Ohain and constructed by Ernst Heinkel in Germany in 1938. Today, jets dominate air travel due to their speed, ability to fly at higher altitudes, and reliability of their mechanical systems. Jet aircrafts are also able to fly higher to avoid turbulence and increase the number of aircrafts in the sky, as well as carry heavier cargo.