The spy drone lurking above our heads: British-built solar powered aircraft can quietly cruise through the stratosphere for months at a time

It looks like a cross between a toy airplane and a drone, but this British solar-powered aircraft could be the future of aerial surveillance. PHASA-35, built by British company BAE Systems, is a 150kg solar-electric aircraft that can quietly cruise through the stratosphere for months at a time. Named after its 35-metre wingspan, the unmanned aerial vehicle (UAV) travels at a maximum height of 70,000 feet, at a leisurely speed of 55mph. Designed as a cheaper and lighter alternative to satellites, it can be used for Earth observation and surveillance, border control, communications and disaster relief. Now, BAE Systems reveals that PHASA-35 has just completed a second round of test flights into the stratosphere – the second layer of Earth's atmosphere.