In a This Day in History video, learn that on July 27, 1949, the world's first commercial jet liner took to the skies over England. The Comet ran a spectacular test run and was a far cry from what travelers were used to. The commercial jet flew fast and high while breaking all molds. Unfortunately, a structural defect caused two comets to break up in midair. Other manufacturers improved on the Comet's technology and jet-powered travel took off.