The United States delivered its first shipment of F-35 stealth fighter jets to Turkey, despite tensions with the country and US lawmakers’ opposition.

American defense giant Lockheed Martin officially transferred possession of the first plane, designed to evade even the most advanced radars, to Turkish officials during a ceremony in Fort Worth, Texas.

A second plane is due to be delivered in the coming days and the two aircraft will be brought “at a later date” to Luke air force base in Arizona, where Turkish pilots and maintenance crews are receiving training, said Lieutenant Colonel Mike Andrews, a Pentagon spokesman.

US senators have opposed the delivery in light of Ankara’s plans to purchase Russian S-400 missile defense systems.

In a defense budget bill approved Tuesday, the senate demanded that F-35 sales be scrapped if Turkey goes ahead with the Russian purchase.

If both chambers of the US Congress approve that version of the bill, President Donald Trump’s administration will be obliged to exclude Turkey from the F-35 program, remove from the aircraft all parts made in Turkey and ban the Turkish F-35s from leaving US territory.

Turkey has been a partner in the international consortium that financed the F-35 since 2002.