In 1986, the Federal Aviation Administration formed a contract with three companies to re-engineer a major portion of the New York terminal approach control (TRACON) application software-the software that supports air traffic control in the New York City and Newark, New Jersey, area. This paper discusses the techniques used to successfully re-engineer the soft-ware to run on an IBM System/370", illustrating that real-time software can be logically converted from one computer to another, reliably and cost-effectively.