WASHINGTON (Reuters) - Boeing Co has won a contract valued at up to $750 million over five years for continued work on the U.S. Air Force's fleet of B-1 bombers, the Pentagon announced on Monday. The contract, which includes a one-year base period and four one-year options, covers integrated engineering services such as computer network support, technical analysis, flight safety analysis and possible work on enhancements, the U.S. Defense Department said in its daily digest of major contracts. (Reporting by Andrea Shalal-Esa; Editing by Diane Craft)