The first DC-9 was ordered as part of the pilot training program in 1967. While PSA never did any pilot training on the DC-9, the aircraft was put into revenue service in the interim. Both aircraft were sold off in 1969.
In 1983, four aircraft were purchased from Air Canada to allow rapid growth without purchasing more expensive DC-9-80s. These four aircraft were originally destined for startup airline Altair, but Altair went bankrupt before delivery. PSA operated these planes alongside the DC-9-80s until the merger, when they were added to the large USAir DC-9 fleet.,