#11
Okay, Arrow Air is very close alphabetically but Atlas isn't far enough away. At least I'm headed in the right direction.
However, there are a lack of 72S operators at all, let alone all-economy, meeting the criteria. I think we're looking at different definitions of "very close"!
But there is one more possibility that might make the grade, though I have no idea what their route structure was for their short existence. How about Braniff (as in Braniff III)?