Basically what the question says. TWA seemed to have differing views on the DC-9 at the end of the '70s and the end of the '1980s. They actually retired the Boeing 727-100s I believe soon after the Ozark buyout, and they kept those DC-9s well until they were over 30 years old. TWA ordered a batch of about 20 or so DC-9-10s in the mid-1960s and flew them until around the end of the '70s. I've never figured out why TWA decided to get rid of them...did they favor the 727 more at that time? Even if they were only leased, i'm surprised TWA wasn't more aggressive in pursuing them. Or were they sold for similar reasons that some of the 747s were during the oil crisis: to raise cash?
I'd like to know the answer to this, because quite frankly, I never would've guessed such a large DC-9 operator would have canned its original fleet, only to keep an even greater amount later.