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.