 It remains a considerable engineering challenge to obtain both the power-to-weight ratio and rotor efficiency required to sustain a helicopter in flight.On 13 June 2013, the AeroVelo Atlas was the first to complete a flight that lasted 64 seconds and reached an altitude of 3.3 metres, thus winning the American Helicopter Society (AHS) International's Igor I. Sikorsky Human Powered Helicopter Competition.The American Helicopter Society (AHS) International's Igor I. Sikorsky Human Powered Helicopter Competition was a competition to achieve the first human-powered helicopter flight to reach an altitude of 3 m (10 ft) during a flight lasting at least 60 seconds, while remaining within a 10 m (32.8 ft) x 10 m (32.8 ft) square, and complying with other competition requirements.