Taken to extremes, this slight unease can result in something called Break-off Phenomenon, where the pilot gets the sensation of being removed from the aircraft, often reporting of being outside the cockpit looking in. It is a dissociative psychological reaction classically reported by high altitude, single-pilot, jet fighter pilots, on long transits with little to do but monitor the instuments.
However, helicopter pilots have reported episodes of break-off phenomenon. Typically, it has occurred in level flight at greater than 2,000 feet above ground level on hazy days or on long cross-country missions over featureless terrain. Interestingly, it has been reported by pilots flying side- by-side with other pilots. Radio communications usually alleviate the dissociative symptoms.