The Lockheed Martin F-16 Fighting Falcon has been the mainstay of the U.S. and allied air forces for decades. Over the years, the aircraft has evolved from a lightweight visual range dogfighter into a potent multirole warplane that flies the gamut of missions ranging from the suppression of enemy air defenses to air superiority. Though it has been operational since 1980, the “Viper” continues to evolve and will remain in service with the U.S. Air Force and other militaries for decades to come. But while the F-16 remains a potent fighter, potential adversaries have caught up—the latest Russian aircraft like the Sukhoi Su-35 can match or exceed the Viper in many respects.

While the Su-35 is more of an analogue to the Boeing F-15 Eagle, Russia is selling many more Flankers than MiG-29 Fulcrum derivatives around the world. Indeed, the U.S. Air Force usually has its  “red air” aggressors replicate Flanker variants (usually the Flanker-G) rather than the MiG-29 or its derivatives during large force exercises like Red Flag or Red Flag Alaska. That’s because derivatives of the massive twin-engine Russian jet are amongst the most likely aerial adversaries American pilots might face.

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(This first appeared in 2015). 

The Su-35 is not the most common Flanker derivative, but it is the most capable version built to date. In the right hands—with properly trained pilots and support from ground controllers or an AWACS—the Su-35 is an extremely formidable threat to every Western fighter save for the F-22 Raptor. The F-35 would probably be ok too—if the pilots used its stealth, sensors and networking to their advantage—tactics and training makes all the difference.

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What about the workhorse fleet of F-16s? The Viper doesn’t have the latest upgraded F-15C’s massive active electronically scanned array (AESA) radar nor can the F-16 usually lob the AIM-120 missile from the speeds and altitudes that the Eagle can attain. But then the F-15C was built as a dedicated air superiority fighter. Most in-service F-16s don’t have an AESA installed at all. The UAE’s advanced F-16E/Fs have the APG-80 AESA—which has excellent capability—but that’s a tiny fleet of aircraft. U.S. Air Force F-16s are not currently fitted with an AESA and are at a severe disadvantage versus the Su-35 or other advanced Flanker derivatives.

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The U.S. Air Force is keenly aware of the problem. The service had intended to retrofit 300 or so F-16s with an upgrade called the Combat Avionics Programmed Extension Suite (CAPES), but that program was cancelled because of automatic budget cuts known as sequestration. Nonetheless, the Air Force knows it needs to urgently retrofit the F-16 fleet with new radars sooner rather than later.

Earlier this year, the Air National Guard issued an urgent operational need statement calling for an AESA to be installed in their F-16s performing the homeland defense mission. The radars are needed to track cruise missiles and other small, hard to detect targets. The active Air Force is also aware of the problem and issued a request for information for a new radar for the F-16 fleet in March. That same month, Air Force chief of staff Gen. Mark Welsh told the House Armed Services Committee, “We need to develop an AESA upgrade plan for the entire fleet.”

The U.S. Air Force does not use the F-16 primarily as an air superiority fighter—the air-to-air mission is secondary—the AESA is needed to keep the venerable jet relevant. With an AESA, the F-16 could probably hold its own against the Su-35 at longer ranges—but it would still be a challenge.

At shorter ranges, it comes down to pilot skill and the performance of each jet’s high off-boresight missiles. The advent of missiles like the R-73 and AIM-9X have turned visual range fights into mutually assured destruction scenarios. Mutual kills are not uncommon during training sorties. While the Su-35’s thrust vectoring gives it an edge at very low speeds (mind you, low speeds mean a low energy state), it’s not an insurmountable problem for an expert F-16 pilot—who knows how to exploit his or her aircraft to the fullest—to overcome.

The bottom line is that the Su-35 and the other advanced Flankers are extremely capable aircraft. The Pentagon’s fourth-generation fighter fleet no longer enjoys a massive technological advantage as they did in years past. The United States must invest in next-generation fighters to replace the existing fleet as soon as possible.   

Dave Majumdar is the defense editor for The National Interest. You can follow him on Twitter: @davemajumdar.