I cannot sing the praises for SW enough.
I am a single dad to a young daughter (at the time of this posting she is 4), traveling alone with her is a scarey thought, but to deal with airplanes as well?

too much! However, the two round trips i've taken with her have both been SW and both could not have been better. The ticket prices are reasonable, esp because I only fly nonstop. I can't seem to find many airlines that even offer Nonstop anymore (plenty of 'direct' but not many nonstop). Add in the two bags per traveler is already included.. that means I can pack up for 4 bags for my daughter and I and not have to worry about not having what we need, or paying luggage fees at an airport, esp since I like to do the magical express @ WDW.
I actually LIKE not having an assigned seat. I tend to get to the airport early and never had less than a B seating. not being assigned ahead of time means I can make a 'snap' judgement about who we sit near... in other words, I can try to sit near another parent and child, so my kid has a buddy to talk with nearby.
I also have a ton of carryons due to medical supplies for myself... SW empolyees have always helped us get everything down the aisle and packed up right in a jiffy so I don't feel like I am in the way, and my daughter can be safely tucked into her seat... no having to feel like I need a million arms as a single parent. SW seems to step in and help so I can focus more on getting my girl settled than worrying about making sure the backpack with snacks doesn't end up on the other end of the plane...
sorry if I seem like I am repeating myself, I am getting tired (3rd shifter) and not sure I am making sense...
in the end, I say GO SW!
