Record-Breaking Flight: AALTO’s Zephyr Soars for 67 Days with Amprius Technology

Amprius Technologies has played a pivotal role in AALTO’s recent achievement of a remarkable 67-day continuous flight using its Zephyr high-altitude pseudo-satellite (HAPS) aircraft, powered by advanced silicon anode lithium-ion batteries.

A New Milestone in Stratospheric flight

In April 2025, AALTO, a subsidiary of Airbus based in the U.K. that specializes in stratospheric unmanned aerial vehicles (UAVs), successfully completed a mission that not only set a new record but also surpassed its previous achievement of 64 days.

Innovative energy Solutions for Extended Flight

Operating at altitudes approaching 70,000 feet, the solar-powered zephyr harnesses sunlight during the day to recharge its battery system. During the night, it relies solely on Amprius’ silicon anode batteries to maintain flight, demonstrating remarkable energy density and durability. This capability marks a meaningful advancement in the realm of long-duration unmanned aerial operations.

Expert Insights on the Achievement

Dr. Kang Sun, CEO of Amprius Technologies, expressed pride in the accomplishment, stating, “We are thrilled to see our batteries facilitate this historic 67-day flight. This achievement highlights the revolutionary potential of our silicon anode battery technology in the aerospace sector. By supplying the necessary energy for Zephyr to operate through the night, our batteries have set a new standard for endurance in stratospheric aircraft. We are privileged to collaborate with AALTO in redefining the capabilities of high-altitude platforms for both commercial and defense purposes.”

Pierre-Antoine Aubourg, Chief Technical Officer at AALTO, remarked, “This 67-day flight represents a significant milestone for both Zephyr and HAPS technology as a whole. The reliable power storage provided by Amprius’ high-energy batteries was crucial for sustaining Zephyr’s operations around the clock. Their technology has been vital in helping us surpass our previous endurance record, proving that continuous stratospheric missions are now feasible. We eagerly anticipate further collaboration with Amprius as we advance our flight program for 2025.”

Transforming the Future of High-Altitude Operations

Amprius Technologies’ batteries are among the few commercially available power sources that meet the stringent energy and weight requirements necessary for sustained HAPS missions. This accomplished partnership between Amprius and AALTO builds on earlier successes, including the 64-day flight in 2022, further affirming the reliability and performance of the Zephyr system and its energy storage solutions.

The implications of the Zephyr flight extend far beyond mere records; it opens new avenues for high-altitude pseudo-satellites in both commercial and defense sectors. With the capability to remain airborne for extended periods, Zephyr combines the persistent coverage of satellites with the operational flexibility of UAVs, making it ideal for continuous border surveillance, secure communication networks, environmental monitoring, and other critical missions that require uninterrupted oversight.