BAE Systems Unveils PHASA-35 High-Altitude unmanned aircraftat DSEI 2025

London, September 2025 – At the Defence & Security Equipment International (DSEI) exhibition, BAE Systems and its subsidiary Prismatic Ltd unveiled the PHASA-35, a solar-powered, high-altitude unmanned aircraft designed to operate in the stratosphere for months at a time. The system is set to reshape the future of surveillance, communications, and disaster response by offering a persistent and cost-effective alternative to satellites and conventional aircraft.

Swift Rise to the Stratosphere

The PHASA-35 (Persistent High Altitude Solar Aircraft) was developed in under two years and first flew in 2020. Despite its massive 35-meter wingspan, comparable to an Airbus A320, the aircraft weighs only 150 kilograms, similar to a motorcycle. Built with lightweight composite materials, its solar panels provide energy to rechargeable batteries, enabling continuous day-and-night flight at altitudes above 66,000 feet.

The aircraft has already achieved multiple stratospheric test flights, including a milestone 24-hour mission in 2023 and further long-endurance trials in 2024, proving its ability to remain stable at extreme altitudes.

Endurance and Flexibility

Unlike satellites, which require costly launches and cannot be retrieved, PHASA-35 can take off and land from standard runways, be refurbished, upgraded, and reused. Its endurance is unmatched by conventional aircraft or drones, with the potential to remain airborne for weeks or even months without refueling.

Its modular payload bay, capable of carrying up to 15 kilograms, allows quick adaptation for various missions. From intelligence, surveillance, and reconnaissance (ISR) sensors to communications equipment, the payloads can be swapped or upgraded as technology evolves.

Wide Range of Applications

The potential uses of PHASA-35 span both civilian and military domains:

• Defense & Security: Persistent surveillance, border protection, maritime monitoring, and secure data transmission.

• Communications: Acting as a stratospheric relay to provide 4G/5G mobile coverage, especially in remote or disaster-hit regions.

• Humanitarian & Environmental: Supporting disaster relief operations when ground infrastructure is destroyed, or serving as a platform for climate and environmental monitoring.

Operational Efficiency

The aircraft’s lightweight structure, solar-powered design, and minimal logistical footprint make it cheaper and easier to operate compared to satellite constellations. BAE engineers are already building the next generation of PHASA-35 aircraft with greater energy storage capacity, aiming for missions lasting several months.

Toward Deployment

BAE Systems plans to begin operational activity with PHASA-35 around 2026, with ongoing flight trials pushing further in altitude, duration, and payload capabilities.

A New Frontier

The PHASA-35 represents a new class of high-altitude pseudo-satellites (HAPS)—platforms that bridge the gap between aircraft and satellites. With its endurance, flexibility, and cost-effectiveness, it has the potential to transform how nations approach surveillance, communications, and humanitarian operations.