And last year, defence firm Qinetiq flew a solar-powered plane for 54 hours, smashing the official world record for the longest-duration unmanned flight.
The single-person aircraft came from Switzerland and has made history as a solar-powered plane that could fly overnight, thanks to batteries that are charged up during the day.
Considered the world's most advanced sun-powered plane, the Solar Impulse took off from Moffett Field in Mountain View at first light for a two-hour practice run in advance of a planned multi-city, cross-country tour.
The Solar Impulse considered the world's most-advanced sun-powered plane set down about 12:30 a.m. at Sky Harbor Airport, completing part of a journey that its pilot described as a "milestone" in aviation history.