The civil aviation industry is looking into reduced crew operations(RCO) that would cut today's two-person flight crews down to single-person crews with support from ground-based crews. Shared responsibility across air and ground personnel will require highly reliable and secure data communication with supporting automation, which will be safety-critical for passenger and cargo aircraft. This paper looks at the different types and degrees of authority delegation given from the air to the ground and the ramifications of each, including the safety and security hazards introduced, the mitigation mechanisms for these hazards, and other demands on an RCO system architecture, which would be highly invasive into (almost) all safety-critical avionics. The related areas of unmanned aerial systems and autonomous ground vehicles are reviewed to find problems that RCO may face, and related aviation accident scenarios are described. Potential problems with RCO data communication encryption are identified. This paper concludes with questioning the economic viability of RCO in the light of the expense of overcoming the safety and security hazards it would introduce.