The Bell X-1, originally designated XS-1, was the first aircraft to exceed the speed of sound in controlled, level flight. It was the first of the so-called X-planes, an American series of experimental aircraft designated for testing of new technologies and usually kept highly secret. http://en.wikipedia.org/wiki/Bell_X-1 this model is protected under a "Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 " license
You are free: to Share — to copy, distribute and transmit the work Under the following conditions: Attribution. You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work). Noncommercial. You may not use this work for commercial purposes. No Derivative Works. You may not alter, transform, or build upon this work.