The Mcdonnell Douglas DC-9 is a single-aisle airliner designed by the Douglas Aircraft Company. After introducing their DC-8 in 1959, Douglas approved the smaller, all-new DC-9 for shorter flights on April 8, 1963. The DC-9-10, first plane of the DC-9 series, first flew on February 25, 1965 and gained its type certificate on November 23, and entered service with Delta Air Lines on December 8. With a 5-abreast seating in economy, it had two rear-mounted Pratt & Whitney JT8D turbofans under a T-tail for a cleaner wing, a two-person flight deck and built-in airstairs.