A high-altitude drone being tested in collaboration with the US Army has ended its epic flight just hours before breaking the world record for longest flight duration.
However, the flight fell just hours short of the world record for longest continuous flight of any kind.
Aircraft spotters using the free online tracking software ADSB Exchange noticed the end of the Zephyr's flight
The UAV (ZULU82) was seen circling above Arizona's Yuma Test Range when it suddenly began displaying a vertical descent rate of 4,544 feet.
The US Army has issued an official statement regarding the abrupt termination of the UAV's flight.
The Zephyr S is a type of aircraft known as a "High Altitude Platform Station," also known as a "pseudo-satellite."
These aircraft are designed to fly at altitudes of up to 70,000 feet for extended periods of time (21,336 m)