Virgin Orbit Carrying Out Test Flights

The pylon is attached, and Jeff Foust of SpaceNews has some info on their test flights:

The company disclosed few details about the test flights, but flight tracking services such as Flightradar24 list three flights of the aircraft in recent days, most recently Aug. 27, taking off from the Southern California Logistics Airport in Victorville, California. The flights ranged in duration from one and a half to three and a half hours in airspace over the Mojave Desert and over the Pacific Ocean off the California coast.