Building Stratospace: AALTO invites industry to put their payloads on the Zephyr HAPS platform
October 14, 2025
AALTO is throwing open the doors of the stratosphere. Through its new “Be the Interface” payload campaign, the Farnborough-based high-altitude platform (HAPS) company is inviting aerospace firms, technology start-ups, and research institutions to integrate their own payloads aboard the Zephyr, the world’s longest-endurance solar-electric aircraft.
Pierre-Antoine Aubourg, AALTO’s Chief Technology Officer, says the company wants to make the stratosphere accessible to innovators outside the traditional satellite and defence domains.
“We are on a journey between research and commercialisation, and with this industrialisation, AALTO is opening what we call stratospace,” he explains to AGN. “It’s a completely blue ocean — we have to invent everything.”
While AALTO’s Zephyr platform was originally developed within Airbus, it now stands as an independent enterprise with ambitions to establish a new global stratospheric industry. The payload campaign marks a decisive shift from internal development to open collaboration.
From Farnborough to stratospace with AALTO’s Zephyr platform
The stratospace concept defines the gap between conventional aviation and orbit, roughly 60,000 to 80,000 feet above Earth, where Zephyr operates for months at a time, powered entirely by sunlight. Aubourg says the company is seeking partners across the supply chain to help populate this new domain with ideas, technology, and services.
“We don’t think there’s anything better than using the full potential of industry, whether aerospace or sensors or anything else, to find new ideas and new services,” he explains. “That’s why we’ve opened our interface to create opportunities for anybody who has technology or customers to build success together.”
AALTO is particularly keen to engage with British firms in the Farnborough aerospace cluster, alongside international participants. And the company has already received strong global interest.
“We’ve been approached by about a dozen companies, from as far away as Eastern Australia, and even by universities developing their own payloads,” Aubourg adds. “It’s a mix of satellite and drone developers, sensor makers and research institutions, all exploring feasibility for stratospheric operations.”
New Zephyr payload applications: Connectivity, Earth observation and pollution monitoring
At its simplest, AALTO expects payloads focused on connectivity and Earth observation, two of the most mature applications for high-altitude platforms.
“There is a clear need for connectivity and Earth observation — radio communication interfaces, new cameras, higher-resolution infrared capability — all that can fit on HAPS and open a new era,” Aubourg says.
But more unexpected applications are already emerging.
“We’re also seeing completely new ideas, like monitoring pollution with particle sensors to measure the atmospheric impact of emissions. That wasn’t even on our radar before people came to us with it.”
This collaborative model marks a significant departure from conventional aerospace procurement. Instead of issuing RFIs and RFPs, AALTO is deliberately taking an “out-of-the-box” approach to uncover use cases no one has yet imagined.
Integrating third-party payloads on AALTO’s Zephyr HAPS platform
The Zephyr platform can fly for weeks or even months at altitudes above 65,000 feet, but its operating environment poses unusual technical challenges. Payloads must survive enormous thermal swings and minimal atmospheric pressure while remaining exceptionally light and power-efficient.
“Weight and power consumption are the big constraints,” Aubourg explained. “Temperatures can swing from positive to minus 90 degrees between day and night, with high levels of ozone and UV. The industry has little experience operating there, so we’re sharing what we’ve learned from thousands of flight hours.”
To streamline integration, AALTO has created a standard payload interface for participants, while remaining flexible enough to adapt to novel concepts.
“We’ve designed a standard interface for the campaign, but if someone brings a great idea that sits outside those boundaries, we’ll adapt the architecture to make it happen.”
Zephyr flight testing, certification and commercial demonstration timeline
The first payload integrations will take place in 2026, when Zephyr begins a series of commercial demonstration flights. These will allow partners to validate and refine their technologies ahead of formal certification.
“At the same time as integration, we’ll offer flight opportunities to validate concepts,” Aubourg explains. “These are not just bench tests — we want to fly the payloads.”
Full certification with the UK Civil Aviation Authority is targeted for late 2027, paving the way for true commercial service.
“You cannot deliver commercial service without a certified platform,” Aubourg said. “So demonstrations come first.”
Lessons from Zephyr’s 67-day stratospheric flight
AALTO’s last major milestone came with the 2023 Zephyr flight from Kenya, which remained aloft for 67 days — a world record for an uncrewed, solar-powered aircraft. The aircraft eventually ditched safely after a critical component failure, but Aubourg calls the mission an invaluable learning step.
“We launched from Kenya, crossed more than ten flight information regions, and went through the Inter-Tropical Convergence Zone — nobody had experience inside that,” he recalled.
“We’ve since improved redundancy with the CAA and introduced a new flight-control system. The concept is mature, but work remains to reach full commercial readiness.”
10 Zephyr aircraft already built
AALTO has already built ten Zephyr aircraft, including an instrumented test vehicle, and plans to ramp up production to one every six weeks by 2027.
“We’re convinced the market can support at least one new aircraft every month once operational,” Aubourg said.
To ensure year-round availability, the company plans to add new launch sites alongside its Kenya AALTOport.
“Kenya is a great place, but not usable 365 days a year. We need full-year access to the stratosphere, so we’re exploring sites in Oceania and South America.”
If AALTO succeeds, Zephyr could become the go-to platform for stratospheric research and pre-commercial testing, much as CubeSats opened low-cost access to orbit. The payload campaign is not just a call to suppliers, but an invitation to help define a new layer of the aerospace economy.
“We want to build a sustainable stratospace,” Aubourg concludes. “By opening Zephyr to others, we’re creating the ecosystem that will make it real.”
