The January incident at Ellsworth AFB resulted in the destruction of the $450 million bomber and a rare quadruple ejection of the crew, who were attempting to execute an instrument landing during poor weather.
Athens signed a long-sought letter of offer and acceptance with airframer Lockheed Martin covering 20 F-35 stealth fighters, with options for a further 20 jets.
The joint North American Aerospace Defense Command dispatched fighter aircraft from both the USA and Canada on 24 July to intercept a combined flight of bombers from Russia and China operating in international airspace around Alaska.