A vehicle includes a frame, drive elements configured to drive movements of the frame, and a computer configured to receive mission planning and manual commands and to control operations of the drive elements to operate in a safe mode in which mission commands are accepted but manual commands are refused, a manual mode in which mission commands are refused but manual commands are accepted and an enroute mode. The computer is further configured to only allow mode transitions directly between the safe mode and the manual mode and directly between the safe mode and the enroute mode.