Miller served from 1996-2002 as chairman and CEO of Crown Castle International Corp., the wireless communications company he founded in 1995. He is the founder, chairman, and majority shareholder of M7 Aerospace LP, Intercomp Technologies LLC, and Visual Intelligence, an imaging technologies company. He also served as director of Affiliated Computer Services Inc. from 2008 until 2010 when the company was acquired by Xerox Corp. Also joining the Airgas board is John P. Clancey, age 65, chairman emeritus of the global shipping company, Maersk Inc.