The U.S. Air Force has awarded Boeing [BA] a $2.8 billion contract to upgrade South Korea's fleet of F-15K Slam Eagle fighters, the Defense Department said on Friday. The contract "provides for the design and development of an integrated suite of aircraft systems to support modification of the F-15K aircraft for the Republic of Korea Air Force and Defense Acquisition Program Administration," the Pentagon said. "Work will be performed at St. Louis, Mo. and is expected to be be complete…