No-one likes to think of an aircraft design as being a "failure", most of all the designers and the company marketing department. Nevertheless, there have been some aircraft that have been somewhat south of successful, and this videos goes through the history of 10 of them. It's an interesting trawl through some amazing designs that didn't quite make the cut for a variety of reasons.
The unsuccessful Piper Altaire single-engined jet. (Piper Aircraft)
