The US online media outlet Air Force Times has published a complete breakdown of Washington's fears of supplying F-35 jets to Turkey as the latter plans to acquire Russian S-400 systems.
According to military acquisition researcher at the American Enterprise Institute, Rick Berger, the key problem with S-400 is that it must be connected to a tactical data link, called Link 16, and Identification Friend or Foe systems that would allow it to correctly identify friendly F-35s in the air. If Turkey manages to successfully patch up Russian S-400s to NATO systems, it would mean that the air defence system will get access to encrypted Link 16 codes, F-35 transponder data and emission signatures, allowing it to correctly detect and identify the stealth fighter in the air.
According to Berger, this means that if any of the S-400s, which are interconnected via a military network, manages to leak this data to Moscow because of malware or Russian maintenance specialists then it will render most of the F-35's advantages useless. The same applies to other, less advanced planes, operated by Turkey, he added.
"With the F-35 flying in close proximity to the S-400 system, over time, you could collect sensitive stealth characteristics of this F-35 and learn its detailed stealth capabilities", Berger said.
The researcher added that once Russia or the "highest bidder" obtains Link 16 codes, they will be able to "spoof" transmissions and send fake signals to NATO troops, essentially fooling them.
At the same time, Washington could face problems even if it doesn't supply F-35s to Turkey under the contract, the media outlet indicated. One of the drawbacks will be the need to look for other suppliers for F-35 parts, some of which are made exclusively in Turkey at the moment. Andrew Philip Hunter, a former senior executive at the Department of Defence interviewed by the Air Force Times, indicated that finding alternative producers for them "will put huge costs" on the US, but will also affect the Turkish economy.
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What is more, Ankara could deny US the right to station its troops at the Incirlik Air Base, which Washington actively uses for its Middle East operations, as retaliation for halting F-35 supplies.
"We're kind of sleep walking into this inevitability that Turkey is out of the F-35 programme. If we don't give them the F-35, why would they want our people there", Berger said.
Even if this scenario doesn't come to life, US forces on Incirlik Air Base will still be limited in their manoeuvres. Namely, they won't be able to use F-35s either, if a S-400 is be deployed nearby, as it will still be able to gather info on the F-35's signature.
Hunter noted that the base is not essential for the US, as it can switch to other Middle East states, such as Qatar, where Washington also has a military base. At the same time, Qatar has also shown interest in Russian S-400 systems.
"My guess is our military folks wouldn't be thrilled about that either", Berger said.
Washington has been trying to convince Ankara to drop the S-400 procurement deal with Russia for over a year, but with little success. In his latest interview, Turkish President Recep Tayyip Erdogan noted that Ankara had tried to buy American Patriot systems instead, but the US had failed to give a better offer than Russia and hence Turkey move on with the S-400 option.
The US has repeatedly expressed concern that S-400s in Turkey may compromise F-35 jets and threatened to halt F-35s' supplies to Ankara. According to some reports, Washington has already done so. In the most recent development, US Vice President Mike Pence said that Ankara must choose between the S-400s and its membership in NATO.
READ MORE: US to Continue Training Turkish Pilots on F-35 Jets — Pentagon
Turkey slammed the US for allegedly using the F-35 to "blackmail" Ankara into dropping the S-400s. Erdogan has repeatedly indicated that Turkey will not abandon the deal with Russia and has demanded timely delivery of the American stealth jets.