In November 2009, Royal Saudi Air Force (RSAF) F-15s, along with Saudi Tornados, performed air raids amid the Houthi insurgency in north Yemen. It was the RSAF's first military action over hostile territory since Operation Desert Storm. In October 2010, Saudi Arabia requested 84 F-15SA (Saudi Advanced) fighters, upgrading of its existing F-15S fleet to F-15SA standard, and related equipment and weapons through a Foreign Military Sale (FMS). On 29 December 2011, the U.S. signed a $29.4 billion contract to sell 84 F-15SAs, as well as the F-15S upgrades. In June 2012, an FMS contract for 68 F-15S to F-15SA modification kits was placed with Boeing. On 20 February 2013, the maiden flight of the first new-build F-15SA occurred.