North American NA-335

The North American NA-335 was North American Aviation's entry into the US Air Force's 1960s-1970s F-X program, which would later result in the McDonnell Douglas F-15 Eagle.
The NA-335 resembles the T-10/Su-27, however the NA-335 lacked the gap between the engine nacelles, and only a single vertical fin.

Background

The "F-X" program dates back to 1964, when the General Dynamics F-111 Aardvark first flown, visualized to complement or replace the Republic F-105 Thunderchief and McDonnell Douglas F-4C Phantom II fighter-bombers. As air-to-air combat intensified in the Vietnam War, the United States Air Force required a new air superiority fighter.