I will be doing a little air travel with my (will be) 13 month old by myself (unfortunately DH can't come) in March. We are flying from MI to AZ, unfortunately not on direct flights. How the heck do you bring a carseat along? We have a Britax Marathon, which is not a tiny little seat. Would I check it and have her as a lap child on the flight? Anyone have experience with this? I'm getting nervous that I just made a huge mistake booking this trip...