Q. I am trying to find tips on booking travel with my son who is 17 months old. We'd like to travel cross country in May. I feel I should buy a seat for him since he is very active and big for his age and there's no guarantee that I’d be able to have an empty seat next to me for more space.  What would you suggest we do to be able to travel comfortably and, ideally, at a reasonable fare?  

A. Unfortunately, with planes packed to capacity, it’s unlikely that there will be an empty seat next to you, and if you buy a seat you’ll have to pay the usual adult fare. Another thing to consider is your son's safety. Jets land at high speeds, usually in the 130 to 140 mph range, and they take off at even higher speeds. There’s always the possibility of a sudden stop, and just as you wouldn’t put an infant in your lap while traveling in a car even at much lower speeds (in fact, it’s illegal in most jurisdictions), you shouldn’t do so when traveling in a commercial airliner. In fact, we're surprised that it's still legal to do so. So we suggest putting infants in an approved child seat when flying. In addition to being safer, it will be more comfortable for both mother and child.