Five airships. That's what it takes to watch 30,000 square kilometers, roughly the size of Belgium, from a single base. No pilots, no refueling stops, no satellite delays. Just hydrogen-powered aircraft circling overhead for half a day at a stretch, feeding back imagery that satellites can't match and battery-powered drones can't sustain.

That's the pitch from Kelluu, a Finnish deep tech company that just closed a EUR 15 million Series A led by the NATO Innovation Fund. It's the fund's first investment into a Finnish company, and it lands at a moment when European governments are scrambling to fill gaping holes in their surveillance capabilities.

The round also drew participation from Keen Venture Partners, Gungnir Capital, and Tesi, Finland's national investment company. For a company building what amounts to a persistent eye in the sky, the investor list reads like a deliberate signal: defense money is flowing north.

Airships carry baggage. A century of Hindenburg jokes and failed commercial revivals will do that. But Kelluu isn't trying to move passengers or cargo. It's building unmanned intelligence platforms that can loiter in contested airspace for 12 hours or more, even in Arctic weather conditions that would ground most drone systems.

The company operates the largest fleet of autonomous airships in the world, according to Sifted's reporting. Its aircraft are designed for intelligence, surveillance, and reconnaissance, what defense insiders call ISR. Where satellites offer wide coverage but often lack detail, and drones deliver sharp imagery but burn through batteries in hours, Kelluu's airships split the difference.

Hydrogen propulsion is the key enabler. It gives the airships endurance that lithium-ion systems simply can't deliver at this scale, while keeping the acoustic and thermal signatures low enough to avoid easy detection. In a world where drone-on-drone warfare is evolving by the month, staying quiet and staying aloft are two sides of the same coin.

The math works in Kelluu's favor when you're talking about persistent wide-area monitoring. Five airships covering Belgium-sized territory from a single base is a logistics argument as much as a technology one.

The NATO Innovation Fund doesn't lead many rounds. When it does, it's making a statement about what the alliance thinks it needs. Leading Kelluu's Series A, NATO's first check into a Finnish company, signals that persistent aerial surveillance is moving from nice-to-have to critical infrastructure in allied defense planning.

Finland's geography makes it an obvious testing ground. The country shares a 1,340-kilometer border with Russia. Its Arctic regions are vast, sparsely populated, and almost impossible to monitor with ground-based systems alone. If Kelluu's airships can perform in Finnish winter conditions, they can perform almost anywhere NATO operates.

"The gap between what needs to be watched and what existing platforms can actually watch is widening," said Giuseppe Lacerenza, partner at Keen Venture Partners. "This team was forged on one of Europe's most exposed borders, backed by leadership that has built and scaled before."

Kelluu's CEO and cofounder, Janne Hietala, brings nearly two decades of entrepreneurial experience. His previous company, Valamis Group, grew from a local Finnish developer into a globally recognized digital learning platform. It's an unusual path to defense tech, but the operational playbook, building complex systems and scaling them internationally, translates directly.

Kelluu previously completed two phases of DIANA, NATO's defense accelerator program. That pipeline gave the company early access to military requirements and procurement pathways that most startups spend years trying to unlock. The Series A funding will go toward scaling the fleet and further developing the sensing platform.

The military use case gets the headlines, but Kelluu is deliberately keeping its aperture wide. The same persistent surveillance that tracks troop movements can also spot wildfires before they spread, monitor pipelines across remote terrain, or provide real-time situational awareness during natural disasters.

European defense spending is surging. NATO allies committed to spending 2% of GDP on defense, and many are now overshooting that target. But the civilian applications matter for Kelluu's business model because they provide revenue stability between government contracts, and they expand the addressable market well beyond the defense budget. For a deeper look at how the Nordics are positioning themselves in defense tech, see our earlier reporting on Sensofusion's counter-drone aircraft factory acquisition.

A fleet of hydrogen-powered, autonomous airships monitoring Europe's borders and forests. It sounds like science fiction until you realize the first units are already flying. Kelluu isn't promising the future. It's delivering the present, just from a higher altitude than you'd expect.