High Altitude Platform Systems (HAPS) have gained increasing attention as a tactical tool in the defense sector; however, their adoption as a communication solution has lagged, with several attempts failing due to high costs. With a new generation of active startups and projects in this area, we outline some of the critical hurdles that HAPS—as a communication platform—must overcome, as well as some of the opportunities for their deployments. In our view, HAPS complement low Earth orbit (LEO) satellite systems; therefore, it is not beyond the realm of possibility that the future will see greater investment interest from the satellite sector.
Download the Insight Note to see additional sections on Investments in HAPS, Lessons from Google Loon, Telecommunications Regulations, and a summary of key takeaways.
Evolution of HAPS
HAPS refer to platforms operating in the stratosphere at altitudes between 20–50 km above Earth’s surface, with most positioned between 20-23 km to avoid the stronger stratospheric winds found at higher elevations. This is relatively low compared to LEO satellites (350–2,000 km), but significantly higher than commercial airplanes, which typically cruise at around 10 km altitude.
The concept of HAPS dates back to the 1990s in the context of mobile communications, when manned fixed-wing aircraft with an 8-hour flight time were proposed. However, it quickly became evident that such a proposition would not be seriously considered.
Recent advancements in materials science, manufacturing, solar cells, power storage, AI, and automation have enabled the development of a new generation of HAPS, including fixed-wing aircraft (e.g., Facebook Aquila), airships, and balloons (e.g., Google Loon). Although these ambitious projects were ultimately retired—Aquila in 2018 and Loon in 2021—they helped shape the development of modern HAPS, paving the way for further innovation.
| Criteria | Fixed-Wing HAPS | Airship HAPS | Balloon HAPS |
| Endurance | Weeks to months (solar). | Weeks to months (up to 1 year; buoyancy-driven) | Weeks to months (up to 6 months; buoyancy-driven) |
| Maneuverability | High (dynamic lift, precise navigation) | Moderate (limited propulsion) | Low (wind-dependent) |
| Flight Stability | Moderate (susceptible to gusts, robust control systems) | High (station-keeping capability, wind-resistant envelopes) | Moderate (stable but wind-sensitive) |
| Payload Capacity | Low to moderate (15–50 kg, limited by wing loading) | High (50–250 kg, large volume) | Moderate to high (up to 100 kg, balloon size-dependent) |
| Deployability | Moderate (requires runway/catapult, ground infrastructure) | Low (complex launch, large ground facilities) | High (simple launch, minimal infrastructure) |
| Operational Team Requirements | High (pilots, engineers, maintenance crew) | Moderate (ground crew, fewer flight control needs) | Low (small team, automated systems) |
Type of HAPS.
HAPS fall into two main categories with three platform types: (a) heavier-than-air (HTA), such as fixed-wing aircraft; and (b) lighter-than-air (LTA), including airships and balloons. HTA systems rely on engines, onboard power generation, and storage to produce lift—factors that directly impact endurance. In contrast, LTA platforms use buoyant gases like helium to stay aloft. These fundamental operational differences lead to critical trade-offs affecting performance and cost parameters:
Endurance – The ability to remain aloft for extended periods.
- Maneuverability – The ability to follow precise paths, maintain stability, and adjust positioning or course efficiently.
- Deployability – Refers to the ease of launch, recovery, and integration into existing networks.
- Flight Stability – The ability to maintain a steady position despite stratospheric winds and turbulence (i.e. station-keeping).
- Payload Capacity – The payload determines the applications a HAPS can support, such as communications, surveillance, or scientific missions. While heavier payloads expand utility and diversify use cases or tenants, they may also reduce endurance and maneuverability.
- Operational Team – Teams are required for pre-launch preparation, flight operations, and post-flight maintenance and recovery.
Considering the various trade-offs, we can summarize the differentiation among type of HAPS:
- Fixed-Wing: Best for maneuverability, but limited by payload capacity.
- Airships: Excel in endurance and payload capacity, but complex to deploy.
- Balloons: Cost-effective and rapidly deployable, but lack maneuverability.
Examples of HAPS include:
- Fixed-wing HAPS – Aalto Zephyr (Airbus spin-out), SoftBank-AeroVironment Sunglider and Prismatics’ Phasa-35, Swift Engineering, and Mira Aerospace.
- Airship HAPS – Sceye, Thales Stratobus, and Stratosyst’s Skyrider.
- Balloon HAPS – Stratollite by World View Enterprises, Stratostats by Involve, and Aerostar.
Use Cases in Telecom Services.
There are several notable use cases for HAPS in telecoms. Some widely cited examples include:
- Greenfield Deployments – Extending connectivity to unserved areas, including remote regions in developed markets and emerging markets where terrestrial coverage is cost-prohibitive.
- Network Resiliency & Emergency Services – HAPS provide rapid-deployment connectivity, supporting disaster recovery efforts and complementing temporary terrestrial solutions, such as cell-on-wheels with satellite backhaul.
- Private Networks & IoT – Used in specialized deployments, though cost sensitivity is a key factor in determining feasibility.
- Backhaul Services – Competing with satellite-based solutions, some HAPS offer advantages by maintaining a relatively static position over a given location. Although HAPS theoretically provide lower latency due to their proximity to Earth, the end-to-end delay may not always be significantly lower than LEO satellites—especially if the transport network relies on satellite links, negating any latency benefits.
- Extended Coverage Over the Sea – Functions similarly to greenfield deployments, delivering connectivity to maritime operations and offshore sites.
- Satellite Capacity Augmentation – A less frequently considered use case, primarily due to the relative novelty of modern LEO satellite networks. However, this approach has the potential to drive financial justification for HAPS deployment more effectively than other use cases, as explored further below.
Complementing Satellites.
LEO satellites provide blanket coverage, distributing traffic evenly across the Earth—irrespective of where demand is concentrated. While this ensures global connectivity, it also means that increasing capacity in high-demand areas requires scaling the entire constellation, an expensive and often inefficient approach.
HAPS, on the other hand, deliver targeted, localized capacity without the need for a massive fleet, keeping costs under control. For LEO satellite networks, HAPS serve as a high-impact complement, efficiently reinforcing capacity where it’s needed most.
Similarly, GEO satellite operators can strategically integrate HAPS to boost coverage in key locations, enhancing their multi-orbital strategies for greater flexibility and performance.
Market Acceptance.
Several key challenges must be addressed before HAPS achieve wider market acceptance.
One major regulatory hurdle is spectrum allocation, as described in the Telecommunications Regulations side box. Beyond this, a fundamental question arises: Should HAPS require dedicated spectrum? Sharing spectrum with satellites or terrestrial networks can lead to significant interference at the boundaries between coverage layers. This issue has historically hindered scalable deployments of small cells in terrestrial networks.
A second challenge is spectral efficiency—just as with satellites, HAPS must improve their ability to maximize bandwidth usage. Unlike terrestrial systems, which leverage multiple-antenna techniques to increase capacity, the typical line-of-sight channel between HAPS and user devices does not support such methods. Advancing technical innovations to address this limitation will be crucial in enhancing HAPS’ ability to deliver high-speed broadband effectively.
Three days after I published this article, Sceye announced a $15m investment from SoftBank. SoftBank plans to launch pre-commercial HAPS services in Japan in 2026, focused on disaster recovery and network resiliency. While SoftBank operates its own HTA program through HAPSMobile, the investment in Sceye’s LTA system serves as a complementary addition to its broader high-altitude platform strategy.