Strangely enough, when there were five carriers competing on PHL-ATL and with DL operating the most frequency (11x daily), it was DL that was charging the highest and getting the fare premium. It was AA that dropped it's fares in attempt to crush competition, selling low walk up fares. It's a weaker carrier on that route, and it had the most to lose. Frontier has pulled out and it's down to four carriers with NK also in, but DL rarely went as low in fares as AA or WN in faring.

In a DL vs. WN vs. B6 match up on BOS-ATL, fares will probably drop and stimulation would happen, but I don't believe fare reduction would be as drastic as I've seen on PHL-ATL. I'd expect NK to drop out or go seasonal. The winter months are hardest. While ATL is warmer than the NE in the Winter, it's still cold there at that time, and not like Florida to stimulate crowds. Winter months would be the hardest for B6, with it not being able to connect pax through ATL generally. However, it might be possible running the flight as a one-stop down to FLL: BOS-ATL-FLL, if B6 does that, to help load factors which would likely be weaker especially in the Winter months.