Lockheed Martin F-35B Lightning II is the short takeoff and vertical landing (STOVL) variant of the aircraft. Similar in size to the A variant, the B sacrifices some fuel volume for a vertical flight system. Vertical flight is by far the riskiest, and in the end, a decisive factor in design. Like the AV-8B Harrier II, the B's guns will be carried in a ventral pod.
On June 11th test pilot Graham Tomlinson, a former Royal Air Force Harrier pilot now employed by BAE Systems, performed a conventional takeoff at 10:17 a.m. CDT from Lockheed Martin’s Fort Worth facility. As planned, all initial F-35B flights will be made using conventional takeoffs and landings, with transitions to short takeoffs, hovers and vertical landings beginning early next year. Tomlinson guided the jet to 15,000 feet and performed a series of handling tests, engine-power variations and subsystems checks before landing at 11:01 a.m. CDT.
info from Lockheed Martin press release
original footage: http://www.youtube.com/watch?v=XIsIzjVi7j4
related: F35 Lightning II compilation http://www.youtube.com/watch?v=dAdKzchkQ2Mhttp://www.youtube.com/watch?v=HDVxlPX0bp4