DROID aircraft collision avoidance tests. NASA's Dryden Remotely Operated Integrated Drone (DROID) aircraft in flight during testing of a ground collision avoidance system. The Automatic Collision Avoidance Technology (ACAT) project's Auto GCAS (Automatic Ground Collision Avoidance System) software has been tested on fighter jets, but can also be used on smaller, radio-controlled aircraft. The DROID aircraft was flown with a smartphone containing the collision avoidance software connected to its autopilot to enable automatic fly-ups or turns when the aircraft neared the ground or a ridge. Photographed on 31 May 2012.