S - Supersonic/Special Test Aircraft

Model Designation Manufacturer Engine(s) Crew Other
XS-1
Bell 1 Reaction Motors XLR11 1 X-1
XS-2
Bell 1 Curtiss-Wright LR25-CW-1 1 X-2
XS-3 Stiletto Douglas 2 Westinghouse J34 1 X-3
XS-4 Bantam Northrop 2 Westinghouse J30 1 X-4
XS-5
Bell 1 Allison J35-A-17 1 X-5