How to prep kid for a flight?

My babies first flight was at 3 months old. And it turned out great. He slept through the whole flight of 2 and a half hours. What I did was before we board the plane, I changed his diaper. I calculated the estimated timing for his next feeding and tried to feed him when the plane is about to take off , he will fall asleep. And it works every time we fly together. Btw I’m traveling with just my baby and me back then.

How old is your child?