Vertical Aerospace has commenced the final stage of its VX4 prototype flight-test program, ‘Phase 4 – Transition,’ after receiving its Permit to Fly from the UK Civil Aviation Authority (CAA).
This regulatory approval enables the flight-test team to begin testing the VX4 prototype’s defining transition maneuver, which involves seamlessly shifting between hover (“helicopter mode”) and wingborne flight (“airplane mode”).
Vertical’s Test Pilot, Paul Stone, flew the first flight of this phase on November 13, 2025. This phase follows the completion of flight test Phases 1-3 earlier in the year, which confirmed the VX4’s flying qualities and included flying in open air space for the first time.
To prepare for piloted transition flight, Vertical’s engineering and test teams completed extensive simulation, ground, and flight testing in collaboration with the UK CAA, verifying all 200 Minimum Safe Aircraft requirements. In support of the Permit to Fly, more than 20,000 pages of safety and technical information were updated and submitted to the CAA.
Stuart Simpson, CEO, Vertical Aerospace, said, “Receiving our Permit to Fly and starting Phase 4 marks a defining moment for Vertical Aerospace. Our team has spent months verifying every core system under close regulatory oversight, reflecting our unique and robust approach to certification. This step is a critical demonstration of the VX4’s unique tiltrotor capability and real-world capability and is a major technical and certification unlock.”
The CAA is working closely with the European Union Aviation Safety Agency (EASA) for their concurrent validation and certification of the VX4 to the highest safety standards required for commercial use.
Vertical Aerospace remains on track to complete transition testing by the end of 2025.
