Based on the world record nomination from Europe Records Institute (EURI) and Decision No. WK/USA.INDIA/705/2021/No.161, World Records Union (WorldKings) officially declared de Havilland Aircraft Company is the "the world's first commercial jet manufacturer" on June 10, 2021.
Known for its innovation, de Havilland was responsible for a number of important aircraft, including the Moth biplane which revolutionised general aviation in the 1920s.
The de Havilland DH 106 Comet was the world's first commercial jet airliner. Developed and manufactured by de Havilland at its Hatfield Aerodrome in Hertfordshire, United Kingdom, the Comet 1 prototype first flew in 1949.
It featured an aerodynamically clean design with four de Havilland Ghost turbojet engines buried in the wing roots, a pressurised cabin, and large square windows. For the era, it offered a relatively quiet, comfortable passenger cabin and was commercially promising at its debut in 1952.
According to en.wikipedia