A team from the University of Toronto in Canada has won a $US250,000 prize for designing a helicopter powered by a human riding a bicycle.
The Igor Sikorsky Human-Powered Helicopter Award was made by the American Helicopter Society. It was awarded for the first time in 33 years.
The Atlas craft has four propellers and a combined wing-span of almost 50 metres, but weighs only 50kg.
"It was long seen as impossible to win this," AHS International executive director Mike Hirschberg told AFP.
''It is sort of like climbing Mount Everest for the first time - to prove it can be done."
In a flight on 13 June, the craft was pedalled by Todd Reichert, 31, an aerodynamics expert and competitive speed skater. He is chief aerodynamicist at a company called AeroVelo, which was created by the university students.
AeroVelo co-founder Cameron Robertson, 26, said the aircraft is designed to be ridden by a fairly strong pedaller.
It requires about one horsepower to operate, when the average person could probably manage 0.5 horsepower, he said.
Mr Robertson said they hope to put what they've learned to other uses - such as very fast bicycles.
The $US250,000 prize, which was formally awarded on Thursday after a technical review of the flight.
The prize is named for Igor Sikorsky, a Russian engineer and pilot who came to America in 1919. In 1939, he designed and flew the world's first successful single main rotor helicopter.