Aviation engineering is a branch of engineering concerned with the design, science and construction of aircraft and spacecraft. It is further divided into two overlapping branches being aeronautical and astronautical. Aeronautical deals with craft which stay and operate within the Earths atmosphere while astronautical deals with craft which operate outside the Earths atmosphere. Aerospace engineering is concerned with the design and construction and application of the science behind the forces and physical properties of rockets, spacecraft, aircraft and other flying craft. It involves aerodynamics characteristics, airfoil, control surfaces, drag, lift and other important properties. Aeronautical engineering was the original term used to describe these practises, but in recent years the broader term aerospace has superseded it in usage, because flight technology has advanced to include flying craft which operate in outer space.