Boeing operates in the both the civilian and military sectors when it comes to the purchase and procurement of their aircraft. Both these sectors operate on the same buying principle and process with a few differences. Military aircraft are usually purchased by governments while civilian aircraft are primarily purchased by airlines or private charter companies. In the aircraft industry, especially for larger bodied aircraft produced by Boeing, aircraft are usually purchased in advance of construction. So Boeing usually receives firm order from a customer before they even deliver the first plane. In many cases they get their orders at the time of the flight and validation of the prototype aircraft. The customers usually express interest to Boeing and firm commitment is obtained on mutually agreeable terms.