British defense, aerospace, and security company BAE Systems and British drone and satellite specialist Prismatic have announced their development of a drone called Phasa-35 Hale UAV (PHASA stands for Persistent High Altitude Solar Aircraft), capable of flights of up to one year. The two British companies have been collaborating on the drone for the past two years. The drone concept has a wingspan of 35 m, yet weighs just 150 kg and operates at a height of approximately 70,000 feet (around 21,000 m). The long flight time is possible thanks to the use of carbon fibers, a new battery technology, and ultra-light solar cells, which charge the batteries through the day sufficiently to allow it to remain in operation overnight.

The two manufacturers say that the PHASA-35 will be suitable for use for communications-related tasks – to improve GPS coverage in remote areas, for example – as well as optical surveillance tasks.

Facebook is also working on unmanned, solar-powered drones, with the aim of providing isolated parts of the world with Internet access. In October 2017 there were also reports of a Russian drone called LA-252, capable of flying and transmitting signals at a height of between 9 and 13 miles (14 to 21 km) for several days.