Phase 4 Flight Testing Underway For VX4 Prototype

Vertical Aerospace, a Bristol, England-based developer of electric aircraft, announced it received its Permit to Fly from the CAA, the UK’s Civil Aviation Authority, and has begun “Phase 4 – Transition” flight testing, the final phase of the flight test program for Vertical’s VX4 prototype.

Regulatory approval for Phase 4 allows Vertical to begin testing the signature maneuver of vertical takeoff and landing aircraft: seamlessly shifting from vertical takeoff and hover (helicopter) mode to wingborne flight or airplane mode.

Paul Stone, Vertical’s test pilot, performed the first flight in Phase 4 in the morning of November 13, 2025.

Vertical completed Phases 1-3 of its flight test program throughout 2025. Those flights validated the handling characteristics of the VX4 and included flights in open airspace.

To obtain the Permit to Fly, Vertical submitted some 20,000 pages of safety and technical data to the CAA, who worked together with EASA, the European Union Aviation Safety Agency. The two agencies certified and validated the VX4 to the very high global safety standards required for commercial use.

Stuart Simpson, CEO of 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. Phase 4 is a critical demonstration of the VX4’s unique tiltrotor capability and a major technical and certification unlock.”

FMI:  vertical-aerospace.com/