"This research addressed the medical requirements necessary for unmanned aircraft (UA) pilots for successful flight in the National Airspace System (NAS). Given that an existing medical certification was recommended, the question of which class of certification to propose was based on the perceived level of risk imposed by the potential incapacitation of the UA pilot. A second-class medical certification was judged to be the most acceptable, considering that there were several factors that mitigated the risk of pilot incapacitation relative to those of manned aircraft. First, factors related to changes in air pressure could be ignored, assuming that control stations for non-military operations would be on the ground. Second, many of the current UA systems have procedures that have been established for lost data link. Lost data link, where the pilot cannot transmit commands to the aircraft, is functionally equivalent to pilot incapacitation. Third, the level of automation of a system determines the criticality of pilot incapacitation because some highly automated systems (e.g., Global Hawk) will continue normal flight whether a pilot is or is not present."
Federal Aviation Administration, DOT/FAA/AM-07/3
Federation of American Scientists: http://www.fas.org/