The E-175 didn't fly until 2002 and the E-190 wasn't available until 2004. Without the 717's, AirTran would have had to keep flying older DC9's at the same fuel efficiency as the 73-200 for at least 5 more years, or buy smaller CRJ7/9's that would have made them more on par with ASA than mainline Delta. The 717 with new first class seats gave AT a new, more fuel efficient, viable product to offer as an alternative to DL pax after 9/11, since all legacy's were dinosaurs headed to extinction. As they made money and all the legacy's downsized on their way to BK, AT had a wet lease agreement with Ryan's 73/320's until they could get their own 73-700's to expand their network, buy/merge with Midwest (who also had 717's) and become enough of a threat to LUV that SWA decided to buy them. I don't think there were any other airframes available in 99-2005 that fit their needs as well as the cheap, used, former TWA 717's sitting on the ramp. I can't remember when MD/Boeing stopped production, but if DL had grabbed the TWA 717's, I think it would have slowed down AT's growth in the 2000's.

Just my opinion, but without the 717, AirTran would not have been success that they were. If we had bought the 717 as the 727/737's were retired, we would have had a mainline 100 seater for the last decade and fewer CRJ 7/9's...and you know how that worked out.