F-35A Lightning II aircraft receive fuel from a KC-10 Extender tanker aircraft from Travis Air Force Base, Calif., during a flight from England to the United States, July 13, 2016. Air Force photo by Staff Sgt. Madelyn Brown
Washington CNN  — 

US senators have launched a new effort to block the transfer of F-35 Joint Strike Fighters to Turkey, a move that comes just minutes after Turkey was scheduled to receive its first jets as part of an official ceremony in Fort Worth, Texas.

A bipartisan group of lawmakers has added an amendment to the Senate’s appropriation bill for the State Department and foreign operations that would prohibit the use of State Department, foreign operations, and related program funds from being used “to transfer, or to facilitate the transfer of, F-35 aircraft to Turkey,” unless the secretary of state certifies that Turkey will not purchase the Russian-made S-400 anti-aircraft missile system.

Although Turkey has long been a participant in the development of the F-35 program, senators have sought to block Turkey from receiving the stealth warplanes amid a deterioration of the US-Turkey relationship and concerns over Ankara’s purchase of the Russian-made anti-aircraft system.

Their efforts have drawn criticism from Turkey and resistance from the Pentagon, but a US defense official told CNN that the concern is that the Russian-made S-400, particularly if it’s plugged into Turkey’s integrated air defense system, could gather technical data on the F-35’s capabilities and that critical information could be passed to Moscow either intentionally or unintentionally through a back door in the Russian designed system.

‘It’s totally nuts’

Those worries were echoed by senators sponsoring the bill.

“The concern is that the F-35 is the most advanced aircraft, the most advanced NATO aircraft, and if Turkey goes forward with the acquisition of the S-400, it will allow the Russians to collect information on how to best attack an F-35 fighter,” Sen. Chris Van Hollen, a Maryland Democrat and one of the amendment’s co-sponsors, told CNN.

“It’s totally nuts to hand the Russian the keys to the mission capabilities of the F-35 and allow them to try to detect and then exploit any vulnerabilities,” he added.

Turkey will technically take ownership of the warplanes on Thursday, but the US will retain custody of the jets while Turkish pilots and maintainers are being trained on the new planes at Luke Air Force Base in Arizona.

A US defense official told CNN that this training program could take one to two years to complete, meaning congressional efforts to block the transfer could still succeed during this period, despite Thursday’s ceremony.

A US official familiar with the process tells CNN that because Turkey is a member of the F-35 consortium, the State Department funding is not involved in the transfer of the aircraft and that the Department of Defense is the lead US agency. While this calls into question the impact of Thursday’s amendment, a significant section of Congress appears intent on blocking the transfer anyway it can.

But a Democratic congressional official argued that the funding block could have an impact, noting that it would prevent the administration from issuing the necessary permits that would allow the planes to actually leave the US. The official also said the State Department played a critical role in approving and facilitating the transfer of every supporting article for the F-35 program

“There’s no way to continue with this transfer without State Department involvement or approval,” the official said.

The defense official said that one potential blocking mechanism could include denying Turkey access to critical software updates, including updated to the Automatic Logistics Information System that the jet requires to function.

US Air Force Lt. Col. Mike Andrews, a spokesman for the Pentagon, told CNN Tuesday that Turkish F-35 pilots and maintainers have already arrived at Luke Air Force Base “and will begin flight academics soon.”

US senators have also sought to block Turkey from receiving the stealth warplanes through language in the National Defense Authorization Act (NDAA) amid a deterioration of the US-Turkey relationship.

While Andrews told CNN Thursday that “the Department of Defense does not comment on proposed legislation,” he did say that, “Turkey’s ongoing S-400 acquisition has the potential to result in US sanctions, additional congressional holds on arms sales, the loss of US-Turkey defense industrial cooperation and a reassessment of Turkey’s participation in the Joint Strike Fighter program.”

An administration official told CNN that the US is actively working with Ankara to offer US and NATO manufactured alternatives to the S-400 air defines system.

Mattis at work behind the scenes

A US defense official told CNN Tuesday that Secretary of Defense Jim Mattis was opposed to congressional attempts to block Turkey’s receipt of the advanced warplanes. The official said Mattis has been actively engaging with members of Congress behind the scenes, in an attempt to ensure similar efforts to block the transfer were removed from the final version of the NDAA.

The transfer of the first aircraft to Turkey was scheduled to take place Thursday at 11:00 EST during a ceremony at Fort Worth, Texas. The planes will then be transferred to Luke Air Force Base in Arizona where pilot training for the F-35 variant takes place.

Congressional efforts to block the sale to Turkey over its purchase of the S-400 have drawn criticism from Turkish officials.

“We have been in that program, including some joint production, production of the parts of F-35s in Turkey,” Turkish Foreign Minister Mevlüt Çavuşoğlu told PBS earlier this month.

“Turkey has been paying the installments on time, on due time. And Turkey have met all the requirements, but you cannot cancel this because of the S-400s that we are buying. It is a totally different issue,” he added, saying Turkey should not be forced to choose between the US and Russia.

Showing its a good NATO member

While NATO officials have called Ankara’s decision to purchase the S-400 a “national decision,” the alliance has also said that it would be very difficult to integrate the Russian made platform with the NATO air defense system.

Van Hollen told CNN that, “Turkey needs to demonstrate that it is a good loyal NATO member.”

“I hope that they will decide that they want to be a good NATO partner and not expose the United States or our other allies to this kind of unnecessary threat,” he added.

As a program partner, Turkish industries “are eligible to become suppliers to the global F-35 fleet for the life of the program. In total, F-35 industrial opportunities for Turkish companies are expected to reach $12 billion,” according to information posted by Lockheed Martin, the jet’s manufacturer.

The company says Turkey plans to purchase “100 of the F-35A Conventional Takeoff and Landing variant.”

Twelve countries participate in the F-35 program. The nine partner nations that participated in the plane’s development include the US, Turkey, UK, Italy, Netherlands, Canada, Australia, Denmark and Norway. All of these countries except for Canada, Denmark and Turkey already are receiving deliveries of the F-35 aircraft. Israel, Japan and South Korea also have received the jets through foreign military sales.