first hangars were completed in 2007. Tinker celebrated the 30-year anniversary of the E-3 Sentry from 29 June to 1 July 2007. Past and present airmen were invited to swap stories and learn about the latest upgrades. On 13 May 2008, Oklahoma County voters voted in favor of $71.5 million in general obligation bonds, the majority of which has been used to purchase the former General Motors Oklahoma City Assembly plant which is located on the southwest section of the base, next to the runway. A 50-year lease-purchase agreement was executed in September 2008 between Oklahoma County and the Air Force, covering the 3.8 million square foot (353,000 m2) facility and surrounding acreage. Oklahoma County officials paid $55 million to buy the plant from General Motors, which is now called the Tinker Aerospace Complex. From 2008 to 2015, the Oklahoma Air National Guard's 137th Air Refueling Wing also assumed an aerial refueling mission in accordance with the 2005 BRAC Recommendations. The then-137th Airlift Wing (ANG) relocated from Will Rogers Air National Guard Base to Tinker AFB, was redesignated as an air refueling wing, and associated with the 507 ARW while its C-130H aircraft were redistributed to other ANG airlift wings. In 2015, the 137th ended its associate relationship with the 507th, was redesignated as the 137th Special Operations Wing (137 SOW), and returned to Will Rogers ANGB, where it operates the MC-12 Liberty aircraft, operationally gained by Air Force Special Operations Command (AFSOC). In 2015, it was announced that the Tinker was in the running for a squadron of the new KC-46A Pegasus. In October, it was announced that the base would not be receiving the plane, which instead was given to the 916th Air Refueling Wing at Seymour Johnson Air Force Base. Tinker was also in competition with Westover Air Reserve Base and Grissom Air Reserve Base for the plane. 25 March 1948 Tornadoes Two large tornadoes struck Tinker Air Force Base, Oklahoma City, Oklahoma, damaging or destroying a large number of aircraft including at least two Douglas C-54 Skymasters, a Douglas C-47 Skytrain, and many Boeing B-29 Superfortresses stored from World War II. In the first storm, "54 aircraft were destroyed, including 17 C-54 transports valued at $500,000 apiece. Also destroyed were 15 P-47 fighters and two B-29 bombers. About 50 other planes were damaged and about 100 vehicles were damaged or destroyed." In the second tornado, "84