Wow, that's impressive.
The military will want to use them as reconnaissance and communications platforms. Civilian and scientific programmes will equip them with small payloads for Earth observation duties.
Their unique selling point is their persistence over a location. Low-Earth orbiting satellites come and go in a swift pass overhead, and the bigger drones now operated by the military still need to return to base at regular intervals for refuelling.
But as Zephyr has now proved, solar UAVs can be left in the sky.
Their solar cells drive propellers during the day and top up their batteries to maintain the craft through the dark hours of night. An autopilot keeps them circling over the same spot.
The latest version of Zephyr is now 50% bigger than its predecessors.
