the official go-ahead. The first free-flying electric helicopter was the Solution F/Chretien Helicopter, developed by Pascal Chretien in Venelles, France. It went from computer-aided design concept on September 10, 2010, to first flight in August 2011, in under a year. In September 2016, Martine Rothblatt and Tier1 Engineering successfully tested an electric-powered helicopter. The five minute flight reached an altitude of with a peak speed of . The Robinson R44 helicopter was modified with two three-phase permanent magnet synchronous YASA Motors, weighing , plus 11 Lithium polymer batteries from Brammo weighing . It later flew for 20 minutes in 2016. On December 7, 2018, Tier 1 Engineering flew an electric, battery-powered R44 over at and an altitude of , setting a Guinness World Record for the farthest distance. In June 2017, Airbus presented its CityAirbus, an electrically powered VTOL aircraft demonstrator. The multirotor aircraft is intended to carry four passengers, with a pilot initially and to become self-piloted when regulations allow. Its first unmanned flight was scheduled for the end of 2018 with manned flights planned to follow in 2019. Type certification and commercial introduction are planned for 2023. Ingenuity, the NASA small uncrewed aerial system (sUAS) which flew on Mars in 2021 to become the first extraterrestrial aircraft, has a single pair of coaxial rotors. The Dragonfly rotorcraft lander should be the second aircraft and rotorcraft to operate on another astronomical object than Earth. It should be flying in the atmosphere of Titan starting around 2034. The VTOL capabilities is incorporated in order to move the lander and its sensors at various locations farther from the landing site. Experimental demonstrators On 21 October 1973, the Militky MB-E1, a Brditschka HB-3 motor glider converted by Fred Militky and piloted by Heino Brditschka, flew for 9 minutes from Linz in Austria: the first electric aircraft to fly under its own power with a person on board, powered by Nickel–cadmium batteries (NiCad). NiCad batteries have a higher energy density than lead-acid batteries, needed to power a heavier than air aircraft. Following successful human-powered flight, a relaunched Kremer prize allowed the crew to store energy before takeoff. In the 1980s several such designs stored electricity generated by pedalling, including the MIT Monarch and the Aerovironment Bionic Bat. The Boeing-led FCD (fuel cell demonstrator) project uses a Diamond HK-36 Super Dimona motor glider as a research test bed for a hydrogen fuel cell powered