An airplane trip is very exciting for kids, especially if they don't often get to fly. If it's been a while since you've traveled with your children, these tips should help you have a smooth flight.
If you are bringing a stroller along, you'll have to remove the child and fold it up (the stroller, not the child!) to go through x-ray. Everyone's shoes will need to come off as well. If you are trying to manage several kids at once, enlist the help of the oldest and let them know in advance what is expected of them. Airport employees are usually happy to help if it gets too much to handle, and often the people in line with you will offer to help.
If you have a baby on formula, take a dry powder form if possible, and add water later. You can buy some water after you go through security.
If you have a very small child that can sit on your lap you won't need to buy an extra seat. However, it might be worth the extra money just to have your hands free. If it's a long flight, holding a small child on your lap will get fatiguing.
If your kids are bringing carry-ons with games and such to occupy them, let them know that you expect them to be responsible and keep up with their stuff. It's real easy to set it down in the waiting area and forget it, or leave it on the plane when disembarking.
If you have an infant, be sure to bring a change of clothes, diapers (bring plenty!), wipes, favorite toys, and maybe a book or two to read to them or, if they are old enough, for them to look through.
For the problem of ear popping, give the kids a piece of gum to chew to help relieve the pressure. Some children are not bothered by it at all.
If you plan to use a car seat on the plane, make sure yours is airline approved (check for a label on the seat).
Be sure to check in early at the airport. It is said that there is never a "too early" at the airport, only a "too late."
Consider a bribe. Dubious but yes it works! Buy each child a new toy and let them know they can't play with it until they are on board the plane. This will occupy them for quite some time!
Let your kids know that while flying they must remain seated with their seatbelt on at all times unless they need to use the restroom. If they already expect this rule, it won't be so hard to enforce once you are on the plane.
Keep your sense of humor! Relax and enjoy the flight and the excitement of your kids.