Complex sentence: Kelly Air Force Base operated out of San Antonio until 2001, when the airfield was transferred over to Lackland AFB and the remaining portions of the base became Port San Antonio, an industrial/business park.
Split into simpler sentences: Kelly Air Force Base operated out of San Antonio until 2001, when the airfield was transferred to Lackland AFB. The remaining portions of the base were developed as Port San Antonio, an industrial/business park.