Spatial Disorientation

A condition in which a pilot's perception of position, attitude, or motion does not match the actual state of the aircraft, caused by the vestibular system being unable to distinguish between gravity and centrifugal force or to sense gradual changes in bank or pitch. It is most common when flying in reduced visibility without reference to the horizon. The FAA emphasizes that pilots must trust their instruments over bodily sensations, as the inner ear can be completely unreliable in flight.