The F-15 Eagle is an icon of the United States Air Force, synonymous with aerial superiority and engineering excellence. Before it entered service, it had to prove that it could fulfill the needs of the Air Force better than the rest. Its competitor has essentially been forgotten, but at one time represented a very exciting design.

The now-defunct plane maker known as North American Aviation (NAA) was once among the leaders of us aerospace companies, pioneering the dawn of the jet age. North American produced one of the fastest jet to ever fly from an aircraft carrier, as well as one of the largest to ever operate from the “boat.” Recognizing their opportunity, the company entered its own design into the F-X competition against McDonnell Douglas’ F-15.

The aircraft that was proposed is known only as the NA-335. Despite its promise of higher performance along with superior capability, it never progressed from the drawing board, and the F-15 won the award. The jet appeared to surpass the F-15 and virtually every point of technical comparison, except one: design risk. That proved to be its undoing, and it was lost to the annals of history.

McDonnell Douglas’ Victory

The Cold War was driving an arms race of epic proportions in the 1960s. At the same time, American fighter pilots from the Air Force and the Navy had just recently experienced their first combat in the jet era. The US and the United Nations had drawn down forces in Korea, but the war in Vietnam was raging at fever pitch. The F-4 Phantom from McDonnell was already being flown as a common airframe among the different service branches of the US armed forces, and despite some issues with maneuverability and weapons, it was strongly favored by aircrew and top brass alike.

That gave the company a leg up against NAA, which at the time only had niche aircraft in its portfolio. This element of institutional entrenchment was highly beneficial for the F-15 program to beat the competition. McDonnell merged with Douglas in 1967, and the combined company’s catalog included highly successful commercial and military aircraft as well as spacecraft. The perceived strength of the planemaker lent it much more confidence from the USAF.

NAA would also merge with Rockwell around the same time the F-X program started to spin up. This merger would win the Advanced Manned Strategic Aircraft (AMSA) program and produce the B-1 Lancer bomber, which is still in service today. The supersonic swing-wing strategic bomber was originally built to carry nuclear weapons and even incorporated some early stealth technology into its design. It is likely that the effort associated with this project put the NA-335 on the back burner and contributed to its failure.

Recent problems with the TFX program had made the service wary. The F-15 was similar to the NA-335 in terms of performance and other features, although the NAA proposal did edge it out slightly in many categories, according to the National Security Journal. Ultimately, the Air Force shows a design that was backed by a reputation for quality and reliability as a hedge against program risk. The F-15 officially won the F-X program on December 23, 1969, and the rest is history.

The F-X Program

The F-4 was a good fighter, but as the Soviet Union advanced designs to be higher flying and faster, the US wanted to stay one step ahead. The F-4 also had a mixed battlefield performance in the sky over Vietnam. The heavy emphasis on speed left it at a disadvantage in maneuverability against light fighters like a MiG-21. It also lacked a gun, and its missiles were not as reliable as anticipated, making it vulnerable in a dogfight. The lessons learned push the Air Force to seek one jet that could win any aerial engagement.

The Air Force also lacked a supersonic fighter that could intercept the latest nuclear-armed bombers and other aircraft of the Soviet Union. The MiG-25 Foxbat could cruise at almost Mach 3 and even reach Mach 3.2 on dashes, while carrying long-range missiles. The USAF simply had nothing like it at the time. The pressure was on, and there was no time to spare with America fearing it might fall behind in the arms race.

From what little information the Department of Defense had, the fox appeared to be an untouchable super-fighter. On that premise, they pursued creating an air superiority fighter that would be capable of outmatching any enemy in the sky. To that end, they did succeed, as the F-15 remains one of the most successful fighter jets ever built, boasting over 100 aerial kills with no combat losses. It was only many years later that they would discover the MiG-25’s limitations were far more severe than they believed.

There was another reason that McDonnell succeeded with their proposal: simple cost. Declassified files from the Office of the Air Force History reveal that just before the contract award was decided, the final review was completed by the Government Accountability Office (GAO). The GAO asked the Air Force to reduce the expected cost per unit of the new F-X fighter by $1.5 million each.

The GAO specifically cited the cost overruns from the F-111 and C-5 competitions as previous failures in previous award evaluations. The cost of the F-15 had already grown over the original budget before even being selected. When the Air Force asked their Fairchild-Hiller, McDonnell-Douglas, and North American to revise their proposals, the winner was the F-15. McDonnell cut its price by $500,000 per plane and beat out the other two despite falling short of the GAO goal.

The Fighter Mafia

The shocking loss of life experienced by American aircrews in the Vietnam War had led a small cadre of engineers, scientists, and fighter pilots to initiate a push against the institutional bias towards heavy, high-powered fighters. The group would become known as “The Fighter Mafia.” They advocated John Boyd and Thomas Christie’s energy-maneuverability (E-M) theory for designing fighter aircraft.

This group was primarily involved in the development of the lightweight fighter (LWF), which would go on to become the General Dynamics F-16 Fighting Falcon. Their influence did extend to be F-X Program and actually favored the NAA design over the others. However, the F-15 was not far behind the NA-335, and eventually, the E-M theories would be applied to the final design of the F-15 that entered production.

The NA-335’s design, which featured a single tail and large folding ventral fins, was seen as technically riskier compared to McDonnell Douglas’s twin-tailed design. There were concerns about stability and control at high angles of attack. North American’s design was even compared to the Soviet T-10 prototype that later became the Sukhoi Su-27 Flanker. Despite the promise that these design features held, fear that the Innovative design would not meet expectations or drag out too long, and development prevented it from leaving the drawing board.

Vigilante Tries Its Hand

North American’s A-5 Vigilante serving the US Navy was famed for its speed and remains the second-fastest jet to fly off a carrier, behind only the legendary F-14 Tomcat. As one of the largest and heaviest USN jets, it was not very maneuverable and notorious for being difficult to land. Its airframe was not designed for air-to-air weapons. That didn’t stop the company from creating new variants based on the jet that was already serving with two radical design modifications that they proposed to the Air Force before and after the F-X Program.

Proposals were sent from Boeing, General Dynamics, Lockheed, McDonnell, North American, and Republic for the Tactical Fighter Experimental (TFX) in 1961. Details of exactly what the company submitted to this competition are not clear, but there is a chance that they submitted a “paper” variant of the A-5, which is known. That plane was known as the NA-247 Retaliator, which replaced the bomb bay in the A-5 with a Rocketdyne XLR46-NA-2 rocket engine. Housed in the aircraft’s linear weapons bay for bursts of extreme high-altitude performance.

Later in 1970, the North American NR-349 was a proposed design submitted to the US Air Force’s Improved Manned Interceptor (IMI) program. This time, the rocket was replaced by a third General Electric J79 engine in an enlarged fuselage. The third powerplant was fed by split intakes on the upper surface to radically boost its speed.

The IMI program sought a replacement for existing interceptors like the Convair F-106 Delta Dart to defend the continental US against potential airborne nuclear threats. The NR-39 has projected capabilities of speeds in excess of Mach 2.5 and altitudes above 80,000 feet. Its armament would have been six AIM-54 Phoenix (like the Northrop Grumman F-14 Tomcat) missiles carried semi-recessed under the fuselage. In the end, the Air Force decided to keep flying the F-106 instead of procuring a new fighter at the time.

North American Hangs It Up

None of the variants of the Vigilante would see success with the Air Force or the Navy. Nor would the NA-335 concept ever be picked up for a new project. In the end, all of these proposed aircraft were shot down. The last successful designs that North American pitched to the Air Force would end up being the supersonic B-1 bomber alongside the small OV-10 Bronco reconnaissance plane.

The Air Force dealt a hard blow to North American when it canceled a number of programs in the 1950s. That included the F-107 and F-108 fighter programs, and the Navaho intercontinental cruise missile program. The fatal Apollo 1 fire in January 1967 also brought intense public scrutiny and initial blame onto the company’s space division.

The NAA XB-70 Valkyrie Mach-3 strategic bomber was a technological marvel that is still romanticized by aviation fans all over the world, but ultimately, it too was canceled. In September 1967, North American Aviation merged with Rockwell-Standard Corporation to form North American Rockwell.

The merged company changed its name to Rockwell International in 1973, and in December 1996, the defense and space divisions of Rockwell International were sold to The Boeing Company. Today, the legacy of North American Aviation lives on as part of Boeing Defense, Space & Security, which integrated the former NAA product lines into its operations.