The most basic of the European unmanned air vehicle specifications is: "For ATM purposes, where it becomes necessary to categorise UAV operations, this should be done on the basis of flight rules, namely instrument flight rules or visual flight rules as applied to operational air traffic."
One of the many implications of this is that UAV ground-based commanders should have all the separation abilities they would have if they were flying a manned aircraft, including the ability, for example, to determine whether visual meteorological conditions are changing to instrument meteorological conditions, and that "UAVs should comply with the right-of-way rules as they apply to any other airspace user".
Finally, in case of the loss of the control link, the UAV must have "a back-up mode of operation that should enable the UAV to revert to autonomous flight in the event of the total loss of the control datalink between the pilot-in-command and the UAV. This back-up mode of operation should ensure the safety of other airspace users." Part of that would be sense-and-avoid capability.
Source: Flight International
