Longest duration Unmanned Aerial Vehicle (UAV) flight
Zephyr S HAPS, Zephyr Programme
623:57:00 hour(s):minute(s):second(s)
United States ()

The longest flight by an unmanned aerial vehicle (UAV) is 25 days 23 hours 57 minutes, set by the Zephyr S HAPS (High Altitude Pseudo-Satellite) over Arizona, USA, between 11 July and 5 August 2018.

The Zephyr S is the latest version of a design that dates back to 2003. It was originally designed by British defence contractor Qinetiq, but the project has been overseen by the European aerospace consortium Airbus since 2013. The goal of the Zephyr program is to create a low-cost, easily deployed alternative to satellites for situations where coverage is needed at short notice.

The aircraft is designed to carry a 24-kg (52-lb) payload, making it possible for it to carry communications relays, terrain mapping systems or signals surveillance equipment. In addition to its military applications, it could be used to provide emergency communications coverage in the aftermath of humanitarian disasters or environmental monitoring.

The Zephyr S does not look like a typical aircraft – it consists of a narrow 25-m (82-ft) wing with a short, slender fuselage that terminates in a T-tail. Despite its size, use of lightweight carbon-fibre composites keep Zephyr's overall weight down to just 75 kg (165 lb).

This combination of low weight and highly efficient aerodynamics allow the craft to fly using just two small electric motors, which have a power drain low enough to be fed by the solar panels built into the skin of the wing and tail. It avoids the requirement for a sturdier frame by flying above the turbulent air of the lower atmosphere, cruising at altitudes of up to 21,561 m (70,740 ft).