 Two American advanced interceptor designs , the Republic XF @-@ 103 and North American XF @-@ 108 , were under development for the United States Air Force as part of their " 1954 Interceptor " ; when both were cancelled in the early design and mock @-@ up phases , it added weight to the justification of cancelling the Arrow . In 1958 , Avro Aircraft Limited president and general manager Fred Smye elicited a promise from the USAF to " supply , free , the fire control system and missiles and if they would allow the free use of their flight test centre at ... Edwards AFB . " 
