A Lockheed Martin F-35 has made more progress in a series of flight tests leading to the programme's first vertical landing.
The company's BF-1 flight-test aircraft on 9 January engaged its short take-off and vertical landing (STOVL) propulsion system at 150kt (277km/h) forward air speed while the aircraft was at an altitude of 5,000ft (1,520m).
During a previous flight conducted on 7 January, the aircraft's shaft-driven lift fan, which powers its STOVL mode, had been activated at 180kt.
Flown by lead STOVL test pilot Graham Tomlinson, BF-1 must eventually lower its forward air speed to 0kt and land vertically. The Joint Strike Fighter programme had originally planned to complete this step in mid-2009, but US Marine Corps officials say the event could now take place as late as June.
Achieving a vertical landing is considered an early landmark event for the F-35 test programme. BF-1 is a flight-test aircraft for one of the three variants that Lockheed is building. No flight-test aircraft are currently operational for either the conventional take-off and landing F-35A or the carrier-based F-35C.
A second STOVL flight test aircraft dubbed BF-2 joined BF-1 at the US Navy's Patuxent River naval base in Maryland earlier this month. The new arrival will remain on the ground at the site to receive modifications until at least late January.