Delta had a total of 17 DC-9-10s. From 1966 thru 1973, when the last -10 was removed from the fleet. FYI, Delta's first DC-9, the second DC-9 built, is still flying with Midwest Express. In service since 1966, this aircraft is older than the first 737, its nearest rival. Since Boeing now owns Douglas Aircraft Corp, perhaps they should purchase the first DC-9, now derelict in Oklahoma, and restore it for historical purposes. Just a thought. Regards.
"Beer is living proof that God loves us and wants us to be happy." --Ben Franklin