The "X" classification in research and development simply marks an invention's current use as "experimental." Some such inventions make it beyond that stage; the majority of those that follow did not. Whatever their contributions to aeronautics in the United States, these X-planes can be appreciated for their interesting designs. 1. The Avrocar Actually Canadian in …

Continue reading Monday at the Museum: 14 X-planes at the National Museum of the U.S. Air Force