Two XF-91 aircraft, serial numbers 46-680 and 46-681, were built by Republic to test, among other things, inverse taper wings, variable incedence wings, and rocket assist power packs. The XF-91 went through several reconfigurations during testing. I have split the pages into the configuration as: original configuration, addition of F-86D-like nose radome and intake, and V-tail configuration. In general, these were known as XF-91, XF-91A, and XF-91B respectively.
Inverse taper swept wings, traditional horizontal and vertical tail, tandem landing gear, rear fuselage ventral rocket installation bulge, oval nose intake.
XF-91 46-680 as it appeared on first roll-out. Republic photo via Jon Brunker.
The second XF-91 46-681 shown in flight with conventional vertical and horzontal tail surfaces, before conversion to V-tail configuration and XF-91A designation. Photo courtesy of AFFTC.
Links to photos at other sites