As one of the posters above said, this really is a case of trial and error. 14 months can be a pretty difficult time to travel for many kids who are recent walkers and who don't understand that they can't walk all the time on an airplane. I personally varied my routine to do whatever seemed easiest for the flight. For me, that meant buying a seat for most flights where I wouldn't have the help of my husband.

In any event, having something to strap the child into is critical for the airport. I'd probably opt for the stroller rather than the car seat cart.