A former Summit Hill man, Thomas John T. J. Leonzi, was killed early today in a plane crash at the Greater Cincinnati International Airport. According to Judy Ingram, a spokeswoman at the airport, Leonzi was the pilot of a Beach B-18 twin-engine aircraft that crashed at 6:20 a.m. about 1,000 feet off the south end of the airport's runway. Ingram said the crash was a result of the left engine stalling in midair. He was the only person on board the aircraft.