U.S. F-35s Have Flown Patrols Over Eastern Europe Without Radar Reflectors

F-35 radar reflectors
U.S. F-35A during refueling. The aircraft does not carry any radar reflectors (U.S. Air Force photo by Airman 1st Class Edgar Grimaldo)

Photos released by the U.S. Air Force prove F-35s have flown in “full stealth mode” over Poland.

On Feb. 27, 2022, we reported that at least one F-35 Lightning II stealth aircraft from Spangdahlem Air Base, Germany, could be tracked online on ADSBExchange.com, as it flew a mission over southeastern Poland, not far from Ukraine. “The track of the F-35 shows that the aircraft operated close to the border with Ukraine, possibly pointing its ESM (Electronic Support Measure) sensors at the Russian forces in Ukraine or Belarus, or simply flying an armed patrol as many of the other NATO aircraft are doing these days” we wrote.

Although it was not the first time an F-35 could be spotted on a flight tracking website or app (it happens quite frequently), the one on Sunday morning marked the first time an F-35’s track appeared over Eastern Europe since Russia had invaded Ukraine.

On the following day, Feb. 28, 2022, U.S. Air Force F-35A aircraft belonging to the 388th FW from Hill Air Force Base flew again over Poland to support NATO’s collective defense. Photographs released by the 86th Airlift Wing/Public Affairs, show two Lightning II jets during AAR (Air-to-Air Refueling) from a KC-135 Stratotanker of the 100th Air Refueling Wing operating out of Ramstein AB, Germany.

Interestingly, the images also show that the F-35s did not carry the usual RCS (Radar Cross Section) enhancers/radar reflectors normally installed during peacetime operations.

Here’s what radar reflectors are, as explained in a previous article this Author posted here at The Aviationist in 2018:

Stealth aircraft, such as the F-22 Raptor or the F-35 Lightning II 5th generation jets are equipped with Luneburg (or Luneberg) lenses: radar reflectors used to make the LO (Low Observable) aircraft (consciously) visible to radars. These devices are installed on the aircraft on the ground are used whenever the aircraft don’t need to evade the radars: during ferry flights when the aircraft use also the transponder in a cooperative way with the ATC (Air Traffic Control) agencies; during training or operative missions that do not require stealthiness; or, more importantly, when the aircraft operate close to the enemy whose ground or flying radars, intelligence gathering sensors.

This is what we explained explaining how the Israeli the heavy presence of Russian radars and ELINT platforms in Syria cause some concern to the Israeli F-35 Adir recently declared IOC:

[…] the Russians are currently able to identify takeoffs from Israeli bases in real-time and might use collected data to “characterize” the F-35’s signature at specific wavelengths as reportedly done with the U.S. F-22s.

In fact, tactical fighter-sized stealth aircraft are built to defeat radar operating at specific frequencies; usually high-frequency bands as C, X, Ku and S band where the radar accuracy is higher (in fact, the higher the frequency, the better is the accuracy of the radar system).

However, once the frequency wavelength exceeds a certain threshold and causes a resonant effect, LO aircraft become increasingly detectable. For instance, ATC radars, that operate at lower-frequency bands are theoretically able to detect a tactical fighter-sized stealth plane whose shape features parts that can cause resonance. Radars that operate at bands below 300 MHz (lower UHF, VHF and HF radars), such as the so-called Over The Horizon (OTH) radars, are believed to be particularly dangerous for stealth planes: although they are not much accurate (because lower frequency implies very large antenna and lower angle accuracy and angle resolution) they can spot stealth planes and be used to guide fighters equipped with IRST towards the direction the LO planes might be.

F-35s deployed abroad usually feature their typical four radar reflectors: to exaggerate their real RCS (Radar Cross Section) and negate the enemy the ability to collect any detail about their LO “signature”. As happened during the short mission to Estonia and then Bulgaria, carried out by the USAF F-35As involved in the type’s first overseas training deployment to Europe or when, on Aug. 30, 2017, four U.S. Marine Corps F-35B Lightning II joined two USAF B-1B Lancers for the JSF’s first show of force against North Korea: the F-35Bs flew with the radar reflectors, a sign they didn’t want their actual radar signature to be exposed to any intelligence gathering sensor in the area

The two radar reflectors installed on the right side of the F-35. The other two are on the other side.

Since they almost always fly with the radar reflectors, photographs of the aircraft without the four notches (two on the upper side and two on the lower side of the fuselage) are particularly interesting: for instance, some shots taken on Jan. 24, 2018 and just released by the U.S. Air Force show F-35As deployed to Kadena AB, Japan, in October as a part of the U.S. Pacific Command’s Theater Security Package program, preparing to launch without their Luneberg reflectors.

F-35s use RCS enhancers to exaggerate their real RCS and negate the enemy the ability to collect any detail about their LO “signature”. Luneberg lenses are also an option in case of war, when enemy air defense assets including sensors, air defense missile and gun systems and enemy aircraft are degraded by airstrikes and the environment becomes more permissive: in such a scenario the F-35 no longer relies on low-observable capabilities for survivability so it can shift to carrying large external loads, and go in a so-called “beast mode”. When the F-35B of the U.S. Marine Fighter Attack Squadron 211, the “Wake Island Avengers”, of the 13th Marine Expeditionary Unit, carried out their first air strike in Afghanistan’s Kandahar Province launching from U.S. Navy Wasp-class amphibious assault ship USS Essex (LHD-2) on station in the Persian Gulf, on Sept. 27, 2018 the jets carried RCS enhancers (and the externally mounted GAU-22 25mm gun pod) in addition to the weapons in the internal bays: in that case, the radar reflectors were carried because there was no need to hide from any Taliban radars over Afghanistan.

That being said, the images taken over Poland prove the situation is different in Eastern Europe and mark the first time U.S. or allied F-35s are spotted operating near enemy airspace without reflectors.

The posture has changed and, as a consequence, the F-35s must be ready, if required, to operate near or inside a contested airspace, in “full stealth mode” to avoid detection from enemy radars. And, again, if you worry about OPSEC, consider that these photos were approved for release and this means that U.S. and NATO want this to be known…

Another image of a U.S. F-35A flying with no RCS enhancers over Poland on Feb. 28, 2022. Image has been digitally altered to highlight the lack of reflectors (original U.S. Air Force photo by Airman 1st Class Edgar Grimaldo)
About David Cenciotti
David Cenciotti is a journalist based in Rome, Italy. He is the Founder and Editor of “The Aviationist”, one of the world’s most famous and read military aviation blogs. Since 1996, he has written for major worldwide magazines, including Air Forces Monthly, Combat Aircraft, and many others, covering aviation, defense, war, industry, intelligence, crime and cyberwar. He has reported from the U.S., Europe, Australia and Syria, and flown several combat planes with different air forces. He is a former 2nd Lt. of the Italian Air Force, a private pilot and a graduate in Computer Engineering. He has written five books and contributed to many more ones.