WutFace

Let me point out the obvious key differences:

1. Southwest had not taken possession / was not operating the B717 at the time they were leased to Delta. Alaska has integrated A320 flight training, maintenance, and operations into their system.
2. Southwest retained ownership of the B717s and is earning revenue on the leases to Delta. Alaska is returning the aircraft as leases expire. In some cases, early with penalty.
3. The B717 and A320/B737 have different missions: One is a small, short range regional, the other is a medium-haul 150+ seat narrowbody.
4. AirTran had 52 737s that it brought with it to the merger. If Alaska dumps the A320s, then they spent 4 billion on basically nothing.

My point stands, every merged airline that had mixed, medium-haul, narrowbody fleets ran the numbers and decided to keep both in the end. Only Alaska thinks it's better to put the toothpaste back into the tube.