For every F-35 Joint Strike Fighter or F-22 Raptor that enters service, there’s a long list of competitor fighters that didn’t quite make the cut for one reason or another. Sometimes, these fighters aren’t chosen because the jet Uncle Sam ultimately picked was simply the better competitor… but that’s not always how these decisions are made.

Like all military forces, the U.S. military has to a balance capability against capacity. In other words, it doesn’t matter if you have 300 of the most advanced fighters on the planet if you need 500 fighters to accomplish your mission, so Defense officials have to balance the cost of the fighter’s advanced capabilities against the capacity (or number) of fighters they need to make mission. In this example, it might mean only purchasing 100 of those advanced fighters along with 400 cheaper, less capable platforms that can meet the mission requirements at hand.

In fact, this specific example (with different topline figures) mirrors the justification the Air Force recently provided for purchasing new F-15EXs, despite its lack of stealth capabilities. In a perfect world, the Air Force would only fly stealth fighters, but when it comes to balancing capability against capacity, stealth jets are just too expensive to buy and operate for America to transition into a stealth-only force.

Other times, fighter programs don’t survive because the Defense Department doesn’t have faith in the contractor to deliver what they promise, or because the capabilities offered by the aircraft aren’t ones the nation has a pressing need for at the time.

For whatever reason, these fighters didn’t make it into production… but if they had, they each would have offered some incredible, and often unique, capabilities.

5. F-16XL: The better F-16

For more than forty years, the F-16 Fighting Falcon has served as the backbone of the U.S. Air Force’s fighter fleet, but one year before the first F-16 entered service, the team behind its development had already developed a better F-16, in the F-16XL.

The fighter was so capable, in fact, that it went from being nothing more than a technology demonstrator to serving as legitimate competition for the venerable F-15E in the Air Force’s Advanced Tactical Fighter program.

Ultimately, it would lose out to the F-15E based on production cost and redundancy of systems, but many still contend that the F-16XL was actually the better platform.

While that assertion may be subject to debate, there’s little debate as to whether the F-16XL could have been one of the most capable 4th generation fighters on the planet. You can read our full feature on the F-16XL’s development here.

4. A-12 Avenger II: America’s first real stealth fighter

On 13 January 1988, a joint team from McDonnell Douglas and General Dynamics was awarded a development contract for what was to become the A-12 Avenger II, not to be confused with Lockheed’s proposed A-12 of the 1960s, which sought to arm an SR-71 sibling jet with air-to-air weapon systems. Once completed, the Navy’s A-12 would have been a flying wing-design reminiscent of Northrop Grumman’s B-2 Spirit or forthcoming B-21 Raider, though much smaller.

Although the A-12 Avenger II utilized a flying wing design, its overall shape differed from the triangular B-2 Spirit under development for the Air Force.

The sharp triangular shape of the A-12 eventually earned it the nickname, “the flying Dorito.“

For some time, it seemed as though the A-12 Avenger II program was going off without a hitch, but then, seemingly without warning, it was canceled by Defense Secretary (and future Vice President of the United States) Dick Cheney in January of 1991. You can read our full feature on the A-12 Avenger II’s development here.

3. YF-12: The biggest, fastest fighter in history

The SR-71 Blackbird may be among the most iconic airframes of the Cold War, but this incredibly fast design wasn’t always intended to serve only as a high-flying set of eyes. In fact, a variant of the SR-71’s predecessor program, the faster and higher flying A-12, actually had a fighter-interceptor sibling in the form of the YF-12, and eventually (in theory at least) the F-12B.

The biggest changes the YF-12 saw when compared to its A-12 sibling were at the front of the aircraft, where a second cockpit was added for a fire control officer tasked with managing the interceptor’s air-to-air arsenal.

The nose was also modified to accommodate the Hughes AN/ASG-18 fire-control radar that had been developed for use in the defunct XF-108 program.

But the most important change between the A-12 and the YF-12 came in the four bays designed originally to house powerful cameras, film, and other reconnaissance equipment. One of the four bays was converted to house fire control equipment, while the others were modified to house an internal payload of three Hughes AIM-47 Falcon air-to-air missiles. You can read our full feature on the YF-12’s development here.

2. ASF-14 Super Tomcat for the 21st Century

While the F-14D took on the title “Super Tomcat,” the effort to modernize the F-14 began under the moniker “ST21,” which, appropriately enough, stood for “Super Tomcat for the 21st Century,” and make no mistake — that’s exactly what it could have been, with improved avionics, more power, more range, and more capability across the board.

But while both the ST21 and AST21 were billed as re-manufacture programs for existing Tomcats along with new-build aircraft, Grumman’s pitch to the Navy eventually included an entirely new-build Tomcat dubbed the ASF-14.

The ASF-14 would have looked like its F-14 predecessors, but the similarities would have been largely skin deep.

The ASF-14, with some 60,000 pounds of thrust and a better thrust-to-weight ratio than the F-14D, thrust vector control, massive internal fuel stores, huge payload capabilities, and incredible situational awareness provided by powerful onboard radar and a multitude of sensor pods, could have been a 4th generation fighter with few — or maybe no — peers to this very day. You can read our full feature on the ASF-14 proposal here.

1. YF-23: The Raptor meets its match

In the decade and a half since it first entered service, the Lockheed Martin F-22 Raptor has been an air superiority fighter without equal, but that hasn’t always been the case. For a short time in the 1990s, the YF-22 that would lead to the operational F-22 may have met its match in the form of Northrop’s YF-23.

Two YF-23 prototypes were ultimately built. The first, dubbed the Black Widow II by those involved with the program, was all black and powered by a pair of Pratt & Whitney engines that allowed the jet to supercruise at Mach 1.43 during its first round of testing in 1990.

The second YF-23, painted grey and dubbed “Grey Ghost,” switched to General Electric YF120 engines, which offered improved supercruise capabilities, reaching Mach 1.6 in testing, just slipping past the YF-22’s Mach 1.58.

Ultimately, while the YF-23 could just about match the F-22’s acrobatics, Lockheed won the perception war by demonstrating their fighter’s capabilities in a more dynamic way. Lockheed test pilots showed off the aircraft’s ability to utilize a high angle of attack, fired missiles, and executed maneuvers that placed more than 9Gs worth of force on the airframe. While the YF-23 could have done the same, Northrop didn’t in the demonstration. Many contend that it was this salesmanship, rather than strictly platform capabilities, that helped the YF-22 stand out in the minds of defense officials. You can read our full feature on the YF-23’s development here.

Alex Hollings is a writer, dad, and Marine veteran who specializes in foreign policy and defense technology analysis. He holds a master’s degree in Communications from Southern New Hampshire University, as well as a bachelor’s degree in Corporate and Organizational Communications from Framingham State University.

This article was originally published by Sandboxx and can be found here.

Image: Reuters