A system for unmanned aircraft system (UAS) testing which incorporates a UAS flight control system and an optionally piloted vehicle (OPV) carrying the UAS flight control system. The OPV has an OPV flight control system and a flight control interpreter (FCI) which receives input from the UAS flight control system representing control parameters for a flight profile of the UAS. The FCI provides status commands as an output to the OPV flight control system to replicate the flight profile. These status commands are selected from the group consisting of data regarding attitude, vertical navigation, lateral navigation, turn rate, velocity and engine operations. The OPV flight control system includes a pilot override for emergency, flight safety or other contingencies allowing an on board pilot to assume control of the OPV.