The Trump administration is requiring the Turkish pilots and maintainers training on the F-35 fighter in the U.S. to leave now that Turkey has been kicked out of the fighter program.

The administration removed Turkey on Wednesday, just days after it began to receive deliveries of Russian S-400 air defense systems. The U.S. has warned the Turkish government that their decision to purchase the S-400 would be incompatible with their NATO commitments, leading to removal from the F-35 program. The pilots and maintainers training in the U.S. will be required to leave as part of the removal.

"All Turkish F-35 students and instructor pilots currently in the United States have firm plans to leave the country," Undersecretary of Defense for Acquisition and Sustainment Ellen Lord said during a Pentagon press briefing on Wednesday. "Roughly 20 Turkish personnel at the Joint Program Office will no longer retain access to JPO spaces."

These actions are intended to mitigate any risks posed to the F-35, according to Lord, and are separate from congressional Russia sanctions.

"All of the pilots knew that we had a July 31 deadline. I just spoke with acting Secretary of the Air Force Donovan a little bit earlier this afternoon and said we were moving forward to suspend Turkey from the program," Lord said. "All of the pilots and maintainers are being notified as we speak."