Spatial disorientation specifically refers to the lack of orientation with regard to the position, attitude, or movement of the airplane in space. The body uses three integrated systems working together to ascertain orientation and movement in space.

• Vestibular system—organs found in the inner ear that sense position by the way we are balanced.
• Somatosensory system—nerves in the skin, muscles, and joints, which, along with hearing, sense position based on gravity, feeling, and sound.
• Visual system—eyes, which sense position based on what is seen.

All this information comes together in the brain and, most of the time, the three streams of information agree, giving a clear idea of where and how the body is moving.
Flying can sometimes cause these systems to supply conflicting information to the brain, which can lead to disorientation. During flight in visual meteorological conditions (VMC), the eyes are the major orientation source and usually prevail over false sensations from other sensory systems. When these visual cues are removed, as they are in instrument meteorological conditions (IMC), false sensations can cause a pilot to quickly become disoriented.

---

Approaching over still water at night - with few external cues (other than runway lights) may lead to glidepath overestimation.