Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of aircraft and spacecraft. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering. The former deals with craft that stay within Earth's atmosphere, and the latter with craft that operate outside it.
Engineering deals with the design, construction, and application of the science behind the forces and physical properties of aircraft, rockets, flying craft, and spacecraft. The field also covers their aerodynamic characteristics and behaviors, airfoil, control surfaces, lift, drag, and other properties. Aerospace engineering is not to be confused with the various other fields of engineering that go into designing these complex craft. For example, the design of aircraft avionics, while certainly part of the system as a whole, would rather be considered electrical engineering, or perhaps computer engineering. The landing gear system on an aircraft may fall into the field of mechanical engineering, and so forth. It is typically a large combination of many disciplines that makes up aeronautical engineering. While aeronautical engineering was the original term, the broader "aerospace" has superseded it in usage, as flight technology advanced to include craft operating in outer space. Aerospace engineering, particularly the astronautics branch, is referred to colloquially as "rocket science". And on duration flights or extra-atmospheric flights, attention also has to be paid to less glamorous and more mundane aspects such as the on-board plumbing. If the aircraft costs multi-millions of dollars, then ensuring crew comfort is not just prudent, but vital. Engineering also covers these more mundane aspects of flight.