The term "Century Fighters" does not include less successful models between the F-100 and F-109 that did not go past design or prototype stage: the Republic XF-103 Thunderwarrior and North American XF-108 Rapier interceptor concepts, the North American YF-107 prototype, and designation "F-109" which was originally assigned to the F-101B Voodoo and later requested but not granted for the Bell XF-109 VTOL concept.