Turkey seeks Russia’s permission to transfer S-400 systems in bid to rejoin US F-35 program
A $2.5 billion defense deal gone sideways could reshape NATO alliances and global defense markets
Turkey has formally requested Russia’s permission to transfer its S-400 air defense systems, a move designed to clear the single biggest obstacle between Ankara and a fleet of American F-35 stealth fighters. The diplomatic maneuver, involving direct conversations between Turkish President Recep Tayyip Erdogan and Russian President Vladimir Putin, represents the most serious attempt yet to unwind a defense deal that has haunted Turkey’s Western alliances for nearly a decade.
The deal that broke everything
Turkey, a NATO member, decided to buy Russia’s S-400 surface-to-air missile system in 2017 for approximately $2.5 billion. By 2019, when Russia began delivering the S-400 batteries, the US kicked Turkey out of the F-35 Joint Strike Fighter program entirely. Turkey had been both a manufacturing partner and a buyer in the program, making the expulsion a significant economic and military blow.
US sanctions followed under CAATSA, the Countering America’s Adversaries Through Sanctions Act, which was specifically designed to punish countries that buy major Russian military equipment.
What’s on the table now
The current diplomatic push started gaining real traction in late 2025. In December of that year, Erdogan raised the idea of returning the S-400 systems during meetings with Putin.
Several options are reportedly being considered. Turkey could declare the S-400 systems inoperable, essentially mothballing them in a way that satisfies US legal requirements. Alternatively, the systems could be relocated to a third country. The most straightforward option would be a complete return to Russia.
As of July 2026, President Trump indicated a willingness to reconsider F-35 sales to Turkey and explore lifting the associated sanctions, provided Turkey no longer possesses or operates the S-400 systems. CAATSA provisions and National Defense Authorization Act language currently prohibit Turkey from accessing the F-35 program while it holds Russian S-400 systems, meaning any deal would likely require congressional involvement.