Following Ankara’s deal to purchase Russian S-400 air defense systems, the Trump administration began removing Turkey from its F-35 stealth fighter program by slowing training for Turkish pilots. Acting US Defense Secretary Patrick Shanahan sent a letter to his Turkish counterpart that laid out the steps for Turkey’s removal from the program unless it changes course. No more trainees will be accepted and those already in the US will have to leave. The US says Turkey’s acquisition of Russia’s S-400s poses a threat to the F-35 stealth fighters, two of which have already been delivered: Turkey cannot have both. Moscow said on Friday that the S-400s destined for Turkey are ready for consignment at the end of July.