NASA's Dryden Flight Research Center is the historic home of the X-Plane program. Originally "XS" for eXperimental Supersonic, these experimental aircraft were built solely for flight research. Flight tests still occur over the Mojave Desert, which provides perfect visibility and flying conditions.

The first X-plane was the Bell X-1, which famously was flown by Chuck Yaeger when he broke the sound barrier on October 14, 1947.

The 1960s saw a raft of experimental aircraft at Dryden. The X-20A Dyna-Soar (Dynamic Soaring) was a delta winged plane, designed to launch into orbit aboard a Titan II rocket. The pre-NASA project was intended to design a bomber aircraft that could skip in and out of the atmosphere and therefore reach its target virtually unopposed. It would return, gliding into land at an airfield. A non-flying prototype completed extensive pre-flight wind tunnel testing and six pilots, including Neil Armstrong, began their training in 1961. However, the project was discontinued in 1963 following huge competition for funding, against the Gemini Project among others.

Although the X-20 Program was never completed and no prototype ever built, much of the design work went on to inform the Space Shuttle Program.