aerial vehicles (UAVs); solar power would enable these to stay aloft for months, becoming a much cheaper means of doing some tasks done today by satellites. In September 2007, the first successful flight for 48h under constant power of a UAV was reported. This is likely to be the first commercial use for photovoltaics in flight. Many demonstration solar aircraft have been built, some of the best known by AeroVironment. Manned solar aircraft Gossamer Penguin Solar Challenger – This aircraft flew from Paris, France, to England on solar power. Sunseeker Duo Solar Impulse – two single-seat aircraft, the second of which circumnavigated the Earth. The first aircraft completed a 26-hour test flight in Switzerland on 8–9 July 2010. The aircraft was flown to a height of nearly by André Borschberg. It flew overnight using battery power. The second aircraft, slightly larger and more powerful, took off from Abu Dhabi in 2015, flew towards India and then eastward across Asia. However, after experiencing battery overheating, it was forced to halt in Hawaii over the winter. In April 2016, it resumed its journey, and completed its circumnavigation of the globe, returning to Abu Dhabi on 26 July 2016. SolarStratos – Swiss stratospheric 2-seater solar plane aims to climb to the stratosphere. Solair – Solair I and Solair II are two German-designed electric aircraft. Hybrid airships Unmanned aerial vehicles Pathfinder and Pathfinder-Plus – This UAV demonstrated that an airplane could stay aloft for an extended period of time fueled purely by solar power. Helios – Derived from the Pathfinder-Plus, this solar cell and fuel cell powered UAV set a world record for flight at . Qinetiq Zephyr – built by Qinetiq, this UAV set the unofficial world record for longest duration unmanned flight at over 82 hours on 31 July 2008. Just 15 days after the Solar Impulse flight mentioned above, on 23 July 2010 the Zephyr, a lightweight unmanned aerial vehicle engineered by the United Kingdom defence firm QinetiQ, claimed the endurance record for an unmanned aerial vehicle. It flew in the skies of Arizona for over two weeks (336 hours). It has also soared to (. China's designed and manufactured UAV successfully reached an altitude of during a test flight in the country's northwest regions. Named "Caihong" (CH), or "Rainbow" in English, it was developed by a research team from CASC. Future projects The BAE Systems PHASA-35 being developed by BAE