Which country was the first to develop and fly a commercial jet airliner?

The first country to develop and fly a commercial jet airliner was, in fact, the United Kingdom, with the introduction of the de Havilland Comet in 1949. This aircraft was significant as it marked the beginning of the jet age for commercial aviation, featuring a pressurized cabin and advanced aerodynamics for its time, allowing for higher cruising altitudes and faster speeds compared to propeller-driven aircraft.

Understanding this context, the development of the Comet revolutionized air travel by paving the way for future commercial jets, influencing aircraft design and technology. While the United States made contributions to the commercial aviation sector, and later, influential aircraft like the Boeing 707 were developed, the Comet's initial flight predates these developments, making the United Kingdom the first nation to achieve this milestone.