Hi! I've traveled a couple times with my now 20 month old but on 2 hour flights. They will most likely fall asleep for the trip, but if they don't, you should be prepared with snacks and something to entertain them with. It also a good idea to take a stroller with you (they let you take it to the gate) and try to keep only what you need on the plane in your carry on so you're not overwhelmed with stuff when you need a bottle to calm your babies on the plane!