The Otto Celera 500L is a business and utility light aircraft developed by American startup, Otto Aviation. By August 2020, 31 test flights had been flown, as introduction is targeted for 2023–2025. It has a single RED A03 diesel piston engine in a pusher configuration and can seat six passengers. History Otto Aviation Group, LLC was established in 2008 by Bill Otto to develop the Celera 500L. William Otto has been a research scientist at Los Alamos Scientific Labs, systems engineer then chief scientist at North American Aviation. Otto Aviation is privately funded since 2008 and is seeking a Series B fundraising round: 200 million dollars are needed for FAR Part 23 certification in three years. Construction of the airplane commenced in 2015. The aerodynamic prototype made its maiden flight in January 2018, and began performance testing in September 2019. Otto publicly announced the aircraft and its development program in August 2020, and noted that 31 test flights had been flown to date. By then, a weight-optimized conforming prototype with cabin windows and longer landing gear was expected to fly within 18 months. FAA certification and deliveries are targeted for 2023–2025. By March 2021, the prototype had achieved over 35 hours of flight tests, interrupted by the pandemic until Q3 2021, before two additional flying prototypes join the program. By October 2021, the company had raised more than $50 million. The prototype should reach a fuel economy of in cruise, to be improved with integrated heat exchangers replacing radiators nacelles. A second turbo-compressor should allow reaching a altitude, and a third for . In 2022, Otto announced a partnership with ZeroAvia to build a hydrogen-powered version of its aircraft. Design The 500L is a mid wing monoplane with a single five blade propeller in a pusher configuration. This results in no aerodynamic interference from the propeller, which is as far back as it can be. Laminar flow is used for its wings, fuselage, and empennage. Otto wants to compete with light business aircraft like the Cessna Citation CJ3+ jet or the Beechcraft King Air 350. The better fuel economy should lead to a low operating cost of $328 hourly. The cabin accommodates six club seats, is about tall, and will be equipped with a lavatory. It is expected to sell for $4.5-5 million, comparable with the HondaJet but with one third its operating cost. Twin-stage turbocharging should enable a cruise