The YB-40s with their numerous heavy modifications had trouble keeping up with the lighter bombers once they had dropped their bombs, so the project was abandoned and finally phased out in July 1943.
På grund af de tunge modifikationer havde YB-40 vanskeligt med at holde trit med de lettere bombere når bombelasten var kastet, så projektet blev udfaset og opgivet i Juli 1943.