I think JetBlue can do better in March than the first two months of Winter on BOS-ATL, mainly because weather becomes milder in March in ATL, daylight savings - longer days to help boost travel, Spring Break and one way car rental deals out of Florida beginning the last week of March, if passengers use it to fly out of ATL.

I don't see Spirit with much lasting power, but it'd be a minor PITB for JetBlue if Spirit decided to re-allocate the fleet to BOS-MCO.

More importantly, if Southwest would continue or concede the route would make a bigger difference for JetBlue.. I think JetBlue can offer the right aircraft for the market, and would be more popular with business passengers based in Boston. Within Southwest's network, I also think Southwest's BOS-BWI already covers most of the connections better than BOS-ATL, with BOS-BNA/HOU/DAL/AUS/MDW/DEN providing additional connections for those that like to go with Southwest connections, even if it's a hassle, for the benefit of lack of change fees and two checked bags. Delta will obviously be there, but JetBlue should do well with Boston based passengers.