The Marine Corps appears on track to have the F-35B STOVL variant reach its Initial Operation Capability (IOC) by July 2015, as it has passed a fairly important milestone.
Recently, six of the new F-35Bs were deployed to the USS Wasp, a small amphibious assault ship which features a smaller landing/takeoff area designed to accommodate rotary wing aircraft and the AV-8B Harrier STOVL aircraft. The first order of business was to check the aircraft and pilot's ability to land on the smaller flight deck of the USS Wasp at night.
While the F-35B features an integrated distributed-aperture system that allows the pilot to see through the aircraft in all-weather nighttime conditions, that system is not approved for use aboard ships yet. Instead, the pilots had use just their naked eye, as well as the F-35B's incredible avionics that make transitioning between horizontal and vertical flight much easier than a comparable aircraft like the AV-8B Harrier.
You can watch a simulation of the aircraft's ability to make the horizontal to vertical flight transition from the cockpit in this video:
The F-35B passed this first test, with all six pilots and aircraft successfully landing aboard the ship 4 times each. There will be more tests coming up, however, as the F-35B continues its march towards a summer IOC.
UPDATE:The first squadron of USMC F-35B's have been declared operational! After passing seven weeks of flight testing, large-force exercises, and operational evaluations involving live ordnance, the Marine Fighter Attack Squadron 121, based out of Yuma, Ariz, are the first operational F-35s in the US military.