US Secretary of Defence James Mattis sent a letter to US Representative Mac Thornberry, chairman of the Armed Services Committee. Mattis acknowledged concerns about the Turkish government but opposed US lawmakers’ efforts to remove the country from the F-35 Lightning II programme, saying the loss of the nation from the supply chain would delay delivery of some aircraft for up to two years.

US top lawmakers objected Turkey receiving the Lockheed Martin F-35 stealth fighter as the country is likely buy Russia’s S-400 Triumf Air Defence system. That surface-to-air missile system is considered one of the most advanced on the export market. Russian Rosoboronexport indicates that it has “anti-stealth range” of up to 81nm.

A bi-partisan group of US Representatives sent a letter to Mattis on 15 June, asking him to block the F-35 deliveries. The US Senate passed the 2019 National Defence Authorisation Act on 18 June with a clause that would also block the aircraft delivery.

Until now, the Department of Defence has been silent on lawmaker opposition to Turkey’s involvement in the F-35 programme.

“Removing Turkey could trigger a supply chain disruption for the US military and our partners, as well as increase other program costs,” Mattis says in his letter to the House Armed Services Committee Chairman on 7 July. “If the Turkish supply chain was disrupted today, it would result in an aircraft production break delaying delivery of 50-75 F-35s and would take approximately 18-24 months to re-source parts and recover.”