The unmanned aerial vehicles are powered by solar cells, recharging batteries in daylight to stay aloft at night.

[3] It was envisionned as an alternative to space satellites, stationed permanently in the stratosphere for environmental monitoring, mobile phone coverage or military applications.

[4] In February 2005, Qinetiq was preparing a demonstration above 30,000 ft for the UK Ministry of Defence at the Woomera Test Range in Australia, for reconnaissance or as a communications relay.

[4] Between 28 and 31 July 2008, in a demonstration for the US military at its Yuma Proving Ground in Arizona, the Zephyr 6 flew for 82 hours and 37 minutes, an unofficial record as the FAI wasn't involved.

[18] The aircraft was lost when one engine component (redesigned since) failed in an unusual high-altitude storm turbulence at 17 km.

[2] In January 2023, the Aalto HAPS company was set up by Airbus to sell its mobile connectivity and earth observation services.

[19] In June 2024, a Japanese consortium led by NTT Docomo and Space Compass committed to invest USD$100m in AALTO to commercialise connectivity HAPS services in Asia, targeting a 2026 introduction.

[20] The 12 m (39 ft) wide aircraft had a carbon composite frame to weigh 12 kg (26 lb), and 1 kW of solar cells powering five motors.

[28] It can be used to perform intelligence, surveillance and reconnaissance (ISR) with a wide visual payload coverage of 20×30 km (12.4×18.6 mi) and can be equipped with radar, LIDAR and infrared technologies.