A solar-powered plane has landed at Washington Dulles International Airport on Sunday to completing the fourth and second-to-last leg of a cross-America flight powered only by the sun.
Solar Impulse took off from St Louis and after a 14-hour stopover in Cincinnati landed in Dulles at 12.15am local time.
The brainchild of Swiss pilots Bertrand Piccard and André Borschberg, Solar Impulse flies at an average pace of 69kmh.
Both pilots take turns flying the plane, which has a single-seat cockpit.
It began its cross-country sojourn on May 3 with an 18-hour-plus flight from northern California to Phoenix.
With the wingspan of a jumbo jet and the same weight as a small car, the Solar Impulse is a test model for a more advanced aircraft the team plans to build to circumnavigate the globe in 2015.
The aircraft runs on about the same power as a motor scooter, propelled by energy collected from 12,000 solar cells built into the wings that simultaneously recharge batteries with a storage capacity equivalent to an electric car.
In that way, the Solar Impulse can fly after dark on solar energy generated during daylight hours. It is the first solar-powered aircraft capable of operating day and night without fuel to attempt a US coast-to-coast flight.