This is a list of aircraft, aviators or air passengers who have disappeared in flight for reasons that have never been definitely determined, particularly in cases where the air frame of the aircraft or body of the person has never been recovered.
It overlaps with Category:Missing aircraft, Category:Missing aviators and Category:Missing air passengers. It does not include combatants who have been posted as “missing in action” during a war or other armed conflict (see Category:Missing in action and Category:Aerial disappearances of military personnel in action.) It does not include once-missing aircraft which have been located.
An aircraft is a machine that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), gliders, and hot air balloons.
The human activity that surrounds aircraft is called aviation. Crewed aircraft are flown by an onboard pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, aircraft propulsion, usage and others.