Stratolaunch ROC Testing To Return Aloft Stratolaunch's ROC is being readied to take to the skies once again. The Stratolaunch ROC is the largest aircraft in the world (by wingspan) and is used to carry testbed payloads. So far the massive aircraft has been out in the open conducting lowspeed taxi tests at the Mojave Air and Space Port (KMHV) this week. Coming up very soon will be the craft's fifth flight test. That will be testing out a new center-mounted pylon from which a hypersonic vehicle will be attached. For the test flight though they will be looking at how the new pylon affects the flight of the Stratolaunch ROC.