Air Commodore Sir Frank Whittle was an engineer, inventor and Royal Air Force officer. He is credited with having invented the turbojet engine. A patent was submitted by Maxime Guillaume in 1921 for a similar invention which was technically unfeasible at the time. Whittle's jet engines were developed some years earlier than those of Germany's Hans von Ohain, who designed the first-to-fly (but never operational) turbojet engine.