By JOSHUA FREED
AP Business Writer

Each day, a little piece of aviation history takes off in Columbus, Ohio. And in Buffalo, N.Y., and dozens of other cities where Northwest flies DC-9s that average 34 years old. Some of them first flew when Lyndon Johnson was president. Northwest's DC-9s tie it for the oldest fleet among the world's 60 largest airlines, even as Northwest adds new planes.

Using Old DC-9s Pays Off for Northwest , continued