Aerospace engineering is the branch of engineering behind the plan, construction and discipline of aircraft and spacecraft. Aerospace engineering has broken down into two major and overlapping branches: aeronautical engineering and astronautical engineering. The earlier deals with craft that wait within Earth's atmosphere and the latter deals with craft those work outside of Earth's atmosphere. While "aeronautical" was the original term, the broader "aerospace" has outdated it in usage, as flight technology higher to include craft in service in outer space. Aerospace engineering is often casually called rocket science.