The only "rule" that I learned the hard way to adhere to was to bring along something for baby to suck on or chew on (depending on baby's age) to clear their ears during takeoff and landing. Best is nursing/bottle for younger babies. If your baby is that age, time feedings before the flight to make sure baby is hungry. An under-2 is too young for gum but there are things they can chew -- gummies, etc. This is for your baby's comfort, it can be very painful.