| Manufacturer | Designation | nickname |
|---|---|---|
| Douglas | D-558 | Skyrocket |
| Bell | X-1 | |
| Bell | X-2 | |
| Douglas | X-3 | Stiletto |
| Northrop | X-4 | |
| Bell | X-5 | |
| Lockheed | X-7 | |
| Bell | X-9 | Shrike |
| North American | X-10 | |
| Ryan | X-13 | Vertijet |
| Bell | X-14 | |
| North American | X-15 | |
| Hiller | X-18 | Propelloplane |
| Curtiss-Wright | X-19 | |
| Boeing | X-20 | Dyna Soar |
| Northrop | X-21 | |
| Bell | X-22 | |
| Martin-Marietta | X-23 | |
| Martin-Marietta | X-24 | |
| Bensen | X-25 | |
| Schweizer/Lockheed | X-26 | |
| Lockheed | X-27 | Lancer |
| Pereira | X-28 | Osprey I |
| Grumman | X-29 | |
| Rockwell | X-30 | NONE |
| Rockwell | X-31 | |
| Boeing | X-32 | TBD |
| Lockheed-Martin | X-35 | TBD |
| McDonnell-Douglas | X-36 | NONE |
| Boeing | X-37 | NONE |
| TBD | X-38 | NONE |