Boeing has completed a series of taxi trials for its Phantom Eye unmanned aircraft in preparation for the liquid hydrogen-powered machine's return to flight.
The aircraft was tested at speeds of up to 40kt (74km/h) on 6 February at Edwards AFB in California.
Boeing has redesigned the aircraft's landing gear since its 1 June 2012 first flight, where it suffered a mishap due its landing digging into the dry lakebed at the desert base. The root cause of the accident was traced to the aircraft's nose gear, which has now been redesigned, Boeing says.
"We've drawn on Boeing's experience using our rugged tactical fighter aircraft landing systems as an example," said Brad Shaw, Boeing's Phantom Eye chief engineer.
Boeing has also completed a number of hardware and software upgrades to enable the aircraft to fly at higher altitudes.
"We have upgraded the autonomous flight systems and have achieved all required test points in preparation for the next flight," says Drew Mallow, Boeing's Phantom Eye programme manager.
The aircraft's next flight is scheduled for later this year.