a sharp reduction in flight hours for crew training since 2005 and the Deputy Chief of Staff for Manpower and Personnel directing Airmen's Time Assessments. On 5 June 2008, Secretary of Defense Robert Gates accepted the resignations of both the Secretary of the Air Force, Michael Wynne, and the Chief of Staff of the Air Force, General T. Michael Moseley. In his decision to fire both men Gates cited "systemic issues associated with... declining Air Force nuclear mission focus and performance". Left unmentioned by Gates was that he had repeatedly clashed with Wynne and Moseley over other important non-nuclear related issues to the service. This followed an investigation into two incidents involving mishandling of nuclear weapons: specifically a nuclear weapons incident aboard a B-52 flight between Minot AFB and Barksdale AFB, and an accidental shipment of nuclear weapons components to Taiwan. To put more emphasis on nuclear assets, the USAF established the nuclear-focused Air Force Global Strike Command on 24 October 2008, which later assumed control of all USAF bomber aircraft. On 26 June 2009, the USAF released a force structure plan that cut fighter aircraft and shifted resources to better support nuclear, irregular and information warfare. On 23 July 2009, The USAF released their Unmanned Aerial System (UAS) Flight Plan, detailing Air Force UAS plans through 2047. One third of the planes that the USAF planned to buy in the future were to be unmanned. According to Air Force Chief Scientist, Dr. Greg Zacharias, the USAF anticipates having hypersonic weapons by the 2020s, hypersonic unmanned aerial vehicles (also known as remotely-piloted vehicles, or RPAs) by the 2030s and recoverable hypersonic RPAs aircraft by the 2040s. Air Force intends to deploy a Sixth-generation jet fighter by the mid–2030s. Conflicts The United States Air Force has been involved in many wars, conflicts and operations using military air operations. The USAF possesses the lineage and heritage of its predecessor organizations, which played a pivotal role in U.S. military operations since 1907: Mexican Expedition as Aviation Section, U.S. Signal Corps World War I as Aviation Section, U.S. Signal Corps and United States Army Air Service World War II as United States Army Air Forces Cold War Korean War Vietnam War Contemporary Historical Examination of Current Operations (CHECO) Operation Eagle Claw (1980 Iranian hostage rescue) Operation Urgent Fury (1983 US invasion of Grenada) Operation El Dorado Canyon (1986 US Bombing of Libya) Operation Just