SoftBank and Sceye test smartphone calls from a HAPS over Japan
SoftBank and Sceye have completed Japan's first communications trial between a high-altitude platform station, or HAPS, and smartphones on the ground. SoftBank announced the result on September 2, 2026.
The platform crossed more than 15,000 km from New Mexico to Japan in about 13 days. Over Muroto City in Kochi Prefecture, the trial carried voice calls, texts, social apps, video calls, video streaming and disaster alerts through a 4G LTE-equivalent base station in the stratosphere.
This was a test, not a consumer launch. SoftBank has not published a plan, price, visitor rule, supported-phone list or commercial coverage map. The company says it is aiming for HAPS commercialization in Japan from 2027 onward.
The traveler answer: the trial proves that a stratospheric platform can connect smartphones in Japan. It does not give a visitor a service they can buy today. For an upcoming trip, use terrestrial mobile data and keep a separate remote-area or emergency backup when the route requires one.
What worked in SoftBank's Japan HAPS trial
SoftBank installed a 4G LTE-equivalent base station on Sceye's lighter-than-air platform. A ground gateway linked it to SoftBank's core network.
| Trial result | What SoftBank reported | What it does not prove |
|---|---|---|
| Smartphone connection | Two-way communication around Muroto City | Compatibility with every phone or visitor account |
| Voice and emergency calls | Stable calls, including Japan Coast Guard number 118 | A public HAPS calling plan or nationwide emergency guarantee |
| Messages and apps | Texts, social apps and disaster-alert messages | Unrestricted access to every app |
| High-capacity data | Video calls and video streaming | A retail speed, allowance or hotspot promise |
| Drone connection | Remote control, location and video data | A consumer drone service |
| Edge computing | 68 ms average round-trip latency in the test | The latency a traveler will receive |
The SoftBank announcement says the platform also carried earthquake and tsunami alert messages. That is relevant to Japan's disaster-resilience plans, but the result remains tied to a controlled area, limited period and selected equipment.
A HAPS is not a satellite
HAPS operates in the stratosphere, at roughly 20 km above Earth. Sceye's vehicle uses helium buoyancy and solar power to remain aloft. SoftBank describes the aircraft as 65 metres long and designed for flights lasting several months.
A direct-to-phone satellite orbits much farther away and moves as part of a constellation. A HAPS can be positioned over a chosen area and behave more like a mobile base station in the sky.
That difference gives each system a distinct role. Satellites can cover very large areas. A HAPS can concentrate capacity closer to one region, with a shorter radio path, but it does not create worldwide coverage from one aircraft.
The new test should therefore not be described as satellite roaming. SoftBank connected smartphones to an airborne platform and then into its mobile core. Our satellite-to-phone status report tracks the separate commercial, trial and planned satellite services.
The Sceye platform flew across the Pacific before the test
The aircraft left New Mexico at 10 p.m. Japan time on August 9. It entered Japanese airspace at 7:11 a.m. on August 23 after flying more than 15,000 km over approximately 13 days.
SoftBank says the HAPS operated off Cape Muroto and held its position within a radius as small as 5 km for an extended period. The communications work took place around Muroto City, an area selected partly to model service restoration after a major disaster.
As of September 2, the platform was flying back toward the United States. The return flight is part of the continuing endurance test, not an expansion of consumer coverage across the Pacific.
Can travelers use SoftBank HAPS in Japan now?
No public signup or roaming route exists. SoftBank has not said whether future access will require a SoftBank account, a specific plan, a particular SIM or eSIM, or a phone bought for the Japanese market.
The missing retail details are important:
- commercial launch date;
- eligible customers and visitors;
- supported phones and software;
- coverage area and service hours;
- price and allowance;
- calls, messages, apps and hotspot terms; and
- international roaming or partner access.
"From 2027 onward" is an aim, not a guaranteed start date. A visitor should wait for a customer offer with published eligibility and coverage before treating HAPS as part of a trip plan.
Why the trial matters for rural routes and disasters
Japan has mountainous terrain, remote islands and areas where restoring a damaged terrestrial network can take time. SoftBank's stated HAPS uses include emergency recovery and coverage where ordinary mobile networks are difficult to reach.
The Muroto trial tested more than a basic text. Voice, alert messaging and video show that the platform carried several kinds of traffic under test conditions. The successful 118 call is especially relevant because 118 reaches the Japan Coast Guard for maritime emergencies.
None of this removes the need for route planning. A future HAPS service will still need aircraft availability, spectrum, backhaul, device support and a customer entitlement. Travelers hiking, sailing or visiting remote islands should continue to follow local emergency guidance and carry the offline or satellite equipment appropriate to the route.
Japan's separate JAPAN Roaming emergency service uses surviving terrestrial carrier networks during designated emergencies. It is not HAPS, and current foreign-line eligibility remains a separate question.
SoftBank's 68 ms edge-computing result
SoftBank also placed a mobile core and web server on the HAPS. Smartphone requests could be processed onboard instead of travelling to a distant internet cloud service.
The company reports an average round-trip latency of 68 ms, more than 40% lower than the cloud route used in the same test. That is a useful engineering result, not a consumer speed guarantee. The comparison does not publish a retail plan, a full set of test conditions or performance across different phones and locations.
For travelers, the practical point is narrower: a HAPS may eventually do more than relay a message. Local processing could support time-sensitive communications and remote operations if SoftBank turns the tested architecture into a commercial service.
SoftBank HAPS or Roaming eSIM for a Japan trip?
They solve different problems. HAPS is being developed for difficult coverage areas and network recovery. A Roaming eSIM uses available terrestrial partner networks for ordinary trip data.
| Travel decision | SoftBank and Sceye HAPS | Roaming eSIM |
|---|---|---|
| Available to buy now | No consumer offer announced | Japan plans are available for compatible, unlocked phones |
| Customer requirement | Not published | Choose a plan from the public catalog |
| Plan terms | No retail price, allowance or validity | Current cards show plan-specific terms before checkout |
| Everyday apps | Demonstrated in a controlled test | General mobile data where a listed partner network is available |
| Remote dead zones | Intended future advantage | No coverage without a supported terrestrial signal |
| Help route | Future customer support not announced | Roaming eSIM publishes 24/7 support |
🏆 Roaming eSIM wins for a trip happening now: the public Japan catalog returned 43 plan records on September 2, with country and regional choices available before departure. SoftBank HAPS wins the test for stratospheric dead-zone potential, but travelers cannot buy that service yet.
A Roaming eSIM does not extend a tower's range and should not be presented as an emergency replacement. Its advantage is current availability and visible package choice. HAPS may later complement terrestrial data if SoftBank publishes a consumer offer.
Choosing mobile data for Japan today
For a one-country trip, start with the Japan Roaming eSIM page. The best eSIM for Japan guide owns the broader provider and plan comparison, including setup, coverage and allowance decisions.
Use a Japan and South Korea Roaming eSIM, Asia 20 Areas Roaming eSIM or Global 120 Areas Roaming eSIM only when its listed destinations match the itinerary. A broader label is not automatically better for a Japan-only trip.
Before buying, check phone compatibility, carrier lock, data allowance, validity, start rule, hotspot support, listed networks and whether the package is reloadable. Download offline maps and save accommodation, transport and emergency details before travelling beyond reliable coverage.
Ten questions travelers ask about Japan's HAPS test
- Is SoftBank HAPS a satellite? No. It is an aircraft operating in the stratosphere at about 20 km altitude.
- Did ordinary smartphones connect? SoftBank reports successful smartphone connections, but it has not published a commercial compatibility list.
- Can a tourist use HAPS in Japan now? No public visitor service or signup route has been announced.
- Does a Roaming eSIM connect to the HAPS? Not under any published term. A Roaming eSIM uses supported terrestrial partner networks.
- Which services worked? Calls, texts, social apps, video calls, video streaming and disaster alerts worked in the trial.
- Did emergency calling work? SoftBank reports successful emergency calls, including 118. This does not establish a public emergency guarantee.
- Will HAPS cover all of rural Japan? No commercial map has been published. The test covered a defined area around Muroto City.
- Does it need a clear view of the sky? SoftBank has not published consumer-use conditions. Future performance will depend on the final network, terrain, buildings and device rules.
- When will SoftBank launch HAPS? The stated aim is commercialization in Japan from 2027 onward, without a firm consumer date.
- Does HAPS replace a Japan Roaming eSIM? No. HAPS targets coverage gaps and recovery; a Roaming eSIM supplies everyday terrestrial data where a supported network is available.
Sources and updates
The trial results, flight details and 2027 aim come from SoftBank's September 2 press release and trial explainer. The platform description and earlier service plan come from SoftBank's HAPS overview and June 2025 announcement.
Update policy: We will update this page when SoftBank publishes a commercial date, coverage map, customer eligibility, supported phones, price, plan features or international-use rules.
