American Airlines will retire its remaining 26 McDonnell Douglas MD-80 aircraft on Sept. 4. The Super 80 aircraft, which American called "the workhorse" of its fleet throughout the 1980s, ceased production two decades ago, and with American's retirement of them, Delta will be the only U.S. carrier that still operates them. American's final revenue flight on the aircraft will be a Sept. 4 flight from Dallas-Fort Worth to Chicago O'Hare.