The United States delivered Thursday 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.
"Any effort by the government of the Republic of Turkey to further enhance their relationship with Russia will degrade the general security of the NATO alliance, and NATO member countries, and degrade interoperability of the alliance," the text reads.
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.
A US defense official stressed that "after aircraft production, the US government maintains custody of the aircraft until custody is transferred to the partner."
"This normally occurs after the lengthy process of foreign partner training is complete (one-two years)," the official added.
Ties between the two NATO allies have been strained since Turkey launched an offensive against Kurdish militia in northeastern Syia -- the People's Protection Units -- that the US backs to fight the Islamic State group but which Ankara considers a terror group.
Launched in the early 1990s, the F-35 is considered the most expensive weapons system in US history, with an estimated cost of some $400 billion and a goal to produce 2,500 aircraft in the coming years.