I’ve heard from a couple of sources that WhiteKnightTwo took off from Mojave Air and Space Port just before 8 am PST (11 am EST) this morning on its second test flight. Look for more details later today.
Update: WK2 landed back at Mojave at 9:22 am PST (12:22 pm EST) according to a source.
Also: more details from Flightglobal.com. Hopefully Will Whitehorn will add some details when he speaks Friday morning at the FAA Commercial Space Transportation conference in Washington DC.