Over the years, a wide range of aircraft designs have been proposed by both Boeing and Airbus. The design principles of several of these proposed programs have helped shape aviation as we know it today, despite never having taken to the skies themselves. Some were too expensive to develop, some arrived at the wrong moment, and others simply failed to attract enough airline interest. In many cases, these aircraft were not bad ideas on paper. From stretched jumbojets designed to rival the Airbus A380 to specialized Dreamliner variants and long-range versions of existing aircraft, these canceled projects show how difficult aircraft development can be. So in this video, we take a look at five commercial aircraft programs from Boeing and Airbus that were ultimately canceled, why they failed to gain traction, and how some of their technology still influences aircraft flying today.