The Solar Impulse has broken its own record for the longest distance flight of a solar-powered aircraft following the second leg of its journey across the USA. Solar Impulse touched down in Texas at 1:08 a.m. local time after a flight of 18 hours 21 minutes having covered at least 868 miles (1,397 km).
Two different distances have been reported for the flight. The Solar Impulse website says the flight "amounted" to 868 miles (1,397 km). However, according to a Phys.org report, Solar Impulse covered a distance of 1,541 km (which it rounds to 950 miles, though this is not the precise conversion).
The difference may be accounted for by a report in Wired that suggests the Solar Impulse was actually flying backwards for parts of its journey due to strong headwinds. In either case, the Solar Impulse has flown more than far enough to break its own previous record for the farthest solar-powered flight, set in May 2012 after a 1,116-km (693-mile) journey from Switzerland to Spain.
According to the official website, pilot and Solar Impulse co-founder André Borschberg was this time able to exploit the aircraft's glider-like design to "surf" updrafts and downdrafts on the way. After sunset the Impulse relies on the altitude it has gained glide powerlessly during hours of darkness.
A flight profile graph released by Solar Impulse suggests the craft managed a small net gain in altitude in an almost 2-hour period up to shortly after 11 pm local time. This approach means it can be beneficial to request permission to fly at altitudes that differ from the norm for local air traffic.
The aircraft is scheduled to complete its next leg to St. Louis by early in June, before subsequent legs to Washington DC and New York, where it is due to land some time in early July. Between legs Solar Impulse is exhibited to visitors.
Source: Solar Impulse