McNabb graduated from the United States Air Force Academy in 1974. A command pilot, he has amassed more than 5,400 flying hours in transport and rotary wing aircraft. He has held command and staff positions at squadron, group, wing, major command and Department of Defense levels. During Operation Desert Shield and Operation Desert Storm, McNabb commanded the 41st Military Airlift Squadron, which earned Military Airlift Command's Airlift Squadron of the Year in 1990. He commanded the 89th Operations Group, overseeing the air transportation of the United States' leaders, including the President, Vice President, Secretary of State and Secretary of Defense. He then served as Commander of the 62nd Airlift Wing. The wing's performance in 1996 earned the Riverside Trophy as the 15th Air Force's outstanding wing. He also commanded the Tanker Airlift Control Center where he planned, scheduled and directed a fleet of more than 1,400 aircraft in support of combat delivery and strategic airlift, air refueling and aeromedical operations around the world. McNabb was then Commander of Air Mobility Command, where he led 134,000 total force Airmen in providing rapid global mobility, aerial refueling, special airlift and aeromedical evacuation for America's armed forces. McNabb's staff assignments have been a variety of planning, programming and logistical duties. These include serving as the Deputy Chief of Staff for Plans and Programs on the Air Staff and Chairman of the Air Force Board having oversight of all Air Force programs. He also served as the Director for Logistics on the Joint Staff where he was responsible for operational logistics and strategic mobility support to the Chairman of the Joint Chiefs of Staff and the Secretary of Defense. General McNabb retired from the Air Force on November 30, 2011 after over 37 years of service.
August 1997 – June 1999, Commander, Tanker Airlift Control Center, Headquarters Air Mobility Command, Scott Air Force Base, Illinois
June 1999 – December 1999, Deputy Director of Programs, Office of the Deputy Chief of Staff for Plans and Programs, Headquarters, United States Air Force, Washington, D.C.
December 1999 – April 2002, Director of Programs, Office of the Deputy Chief of Staff for Plans and Programs, Headquarters, United States Air Force, Washington, D.C.
April 2002 – July 2004, Deputy Chief of Staff for Plans and Programs, Headquarters, United States Air Force, Washington, D.C.
August 2004 – October 2005, Director for Logistics, the Joint Staff, Washington, D.C.
October 2005 – September 2007, Commander, Headquarters Air Mobility Command, Scott Air Force Base, Illinois
September 2007 – September 2008, Vice Chief of Staff, Headquarters, United States Air Force, Washington, D.C.
September 2008 – October 2011, Commander, United States Transportation Command, Scott Air Force Base, Illinois