<p>A hydrogen fuel cell aviation electric propulsion system can meet the dual objectives of extended endurance and carbon reduction. As the power source for the air supply system of the battery cathode, the performance and reliability of the&#xa0;air compressor are critical in determining both the energy efficiency and the lifespan of the aircraft. This investigation presents the design of a hydrogen fuel cell system for a specific type of aircraft, including the development of an ultra-high-speed centrifugal air compressor operating at 150,000&#xa0;rpm. The electromagnetic design of the air compressor’s high-speed motor was completed using the magnetic circuit method, and a finite element framework was established to analyze the&#xa0;electromagnetic and thermal traits of the motor. Besides, the thermal properties and structure of the rotor were analyzed. In the air compressor design, a two-step compression configuration has been taken into consideration, and experimental studies have been conducted towards the assessment of the electromagnetic and aerodynamic performance of the motor, as well as the overall efficiency. The outcomes prove that the&#xa0;centrifugal air compressor design caters to the demands of high-altitude electric reactor inlets, providing a theoretical basis for the subsequent design and enhancement of hydrogen-fueled aircraft.</p> Graphical Abstract <p></p>