 The added weight demanded a much larger wing to allow the aircraft to operate at the required high altitudes.However, to observers, it appeared outwardly similar to the very large F-X studies, an aircraft with high speed and a large wing offering high maneuverability, leading to serious concerns throughout the Department of Defense and the various arms that the US was being outclassed.The MiG-23 was likewise a subject of concern, and it was generally believed to be a better aircraft than the F-4.