Aerospace industry contains various industries including aircraft, spaceships and the jets, engines and rockets production. While defense industry manufactures complementary group of goods, ships and submarines, including tanks, satellites, and armored vehicles, and guns, explosives, bullets.
Both of these industries are closely related to each other. Main source of earning money for aerospace by supplying air planes to individuals or airlines. Commercial Airline Company is infamously cyclical, depending on business cycle, airline fare and terrorism. So rate of purchasing airlines vary.