The Federal Aviation Administration is the final authority on airplanes and safety. Before a rebuilt airplane can take off, it has to be inspected and certified by an FAA inspector as being airworthy. The list of requirements for airworthyness is extremely extensive. The overall goal is to ensure the safety of the pilot and passengers. An airplane must not fail in mid flight, and the FAA wants to ensure that.
Many non-critical used parts are readily available from boneyards. A non-critical part will not affect the airworthyness of an airplane if it fails. For example, a knob on a control lever will not affect the lever if it falls off. Other non-critical parts may include curtains or seat covers. Non-critical parts are in the minority, but are still needed on an airplane rebuilding project.
Critical parts are about 90 percent of an airplane. These include bolts, engines, control cables and instrumentation. Critical parts are governed by the FAA. Many used airplane parts yards, such as the Wentworth yard, sell critical parts. Some of the usable critical parts include engines with low hours or windshields that are not cracked.
Before you consider buying an old airplane to rebuild, think about the cost involved. Airplane parts are not cheap. For example, as of July 2011, a remanufactured engine costs $17,500 out of Wentworth Aircraft. You may pay a small amount for the aircraft itself, but in the end, it might be cheaper to buy a new airplane. You must evaluate the condition of the airplane, especially the framework, before undertaking a rebuilding project.