The McDonnell Douglas DC-9 is an American five-abreast, single-aisle aircraft designed by the Douglas Aircraft Company. It was initially produced as the Douglas DC-9 prior to August 1967, after which point the company had merged with McDonnell Aircraft to become McDonnell Douglas. Following the introduction of its first jetliner, the high-capacity DC-8, in 1959, Douglas was interested in producing an aircraft suited to smaller routes. As early as 1958, design studies were conducted; approval for the DC-9, a smaller all-new jetliner, came on April 8, 1963. The DC-9-10 first flew on February 25, 1965, and gained its type certificate on November 23, to enter service with Delta Air Lines on December 8.