A theoretical airport transit hub, sometimes called “San Diego Grand Central Station,” became more tangible with the head of the Department of the Navy visiting San Diego on Thursday to give the federal government’s go-ahead on planning efforts to redevelop one of its most recognizable properties. Navy Secretary Richard Spencer joined Mayor Kevin Faulconer and the San Diego Association of Governments’ Executive Director Hasan Ikhrata at a media event where they signed an agreement that lays the foundation to remake the Naval Base Point Loma, Old Town Complex. The contract, which supersedes a prior memorandum of understanding, means SANDAG and the Navy can move forward with parallel planning and environmental review efforts of the 70-acre site.