Can anyone give some advice on managing a cross-country flight with my 17 month old? We're planning one from NY to CA soon. She's good, but squirmy, and a recent shorter (two-hour) flight was quite stressful trying to keep her contained, happy and calm. Specifically, would buying her a seat help considerably over holding her as a lap infant? And, if we buoght her a seat, are there any plane-appropriate car seats we could bring and use during the flight, considering she tends to be very calm and happy when harnessed into her car seat during long drives. Thank you very much!