Turkey, one of the original Joint Strike Fighter (JSF) partner nations looks set to be expelled in the next few months.

The US Government’s threat to expel Turkey from the program looks set to be carried out after Turkey refused to cancel its planned acquisition of the Russian Almaz-Antey S-400 Triumf long-range surface-to-air missile system, known as the SA-21 Growler in NATO parlance.

The US’s concern over Turkey operating both the S-400 and the F-35 lies in the advanced capabilities of the S-400’s 92N6A and 96L6E2 radars, and the potential that sensitive radar cross section data about the F-35 could find its way back to Russia.

The US government says it will end Turkish industry contracts on the JSF program in 2020, while the commander of the F-35 training wing at Luke AFB in Arizona has immediately suspended the training of Turkish pilots and maintainers and has revoked their access to the base, ahead of a directed July 31 shut down of the Turkish training program.

“If Turkey procures the S-400…our two countries must develop a plan to discontinue Turkey’s participation in the F-35 program,” acting US Defense Secretary Patrick Shanahan reportedly wrote in a June 6 letter to his Turkish counterpart. “While we seek to maintain our valued relationship, Turkey will not receive the F-35 if Turkey takes delivery of the S-400.”

Turkey has plans to acquire 100 F-35As, and to date has taken delivery of four jets which are at Luke AFB for training, but the US says it has the power to keep the jets from being flown to Turkey.

Turkish industry also manufactures 937 separate components for the F-35, 400 of which are sole-sourced. US Undersecretary of Defense for Acquisition and Sustainment Ellen Lord has said she will aim to achieve a “disciplined and graceful wind down” of Turkish industry participation in order to find alternative suppliers and thus prevent production delays at the F-35 final assembly facilities in Ft Worth, Japan and Italy.

“If we can work to our timelines with the Turks, we would have no major disruptions and very few delays,” she said, adding, “Turkey still has the option to change course. If Turkey does not accept delivery of the S-400, we will enable Turkey to return to normal F-35 program activities. Turkey is a close NATO ally and our military-to-military relationship is strong.”