High-altitude platform developer Sceye has completed a nearly 30,000 km round-trip flight mission between New Mexico in the United States and Japan using its Service Test 1 (ST1) platform. During the flight across the Pacific Ocean, the high-altitude platform system (HAPS) demonstrated direct-to-device mobile connectivity, communications with drones, and onboard data processing capabilities over Japan.
The ST1 mission originally departed from New Mexico on August 9, arriving in Japanese-managed airspace 13 days later. The platform remained over Japan for more than a week before commencing its return trip across the Pacific. It re-entered continental United States airspace on September 4 and reached airspace near Sceye's headquarters in Moriarty, New Mexico, on September 5. The company conducted further vehicle tests before executing a planned termination and descent.
During the mission, Sceye's unmanned lighter-than-air platform operated in the stratosphere at altitudes between approximately 16.5 km and 17 km. The aircraft utilizes solar power during daylight hours and battery storage at night. In collaboration with telecommunications company SoftBank, ST1 carried the SceyeCELL airborne telecommunications payload to demonstrate direct mobile broadband connection to unmodified commercial smartphones. The flight tests encompassed text messaging, voice calls, internet access, video streaming, and disaster alert messaging systems.
In addition to direct smartphone connections, Sceye and SoftBank tested communications between the stratospheric platform and airborne drones off the coast of Japan. During operations in its target zone, ST1 achieved a station-seeking radius as low as 5 km. SoftBank, which previously invested in Sceye's HAPS program in 2025, stated that the test flight increases confidence in developing non-terrestrial three-dimensional networks that integrate ground infrastructure, stratospheric platforms, and satellite constellations.
