A recent article popped up about a family that was ejected from an AirTran flight because of their 3 year old's behavior. Supposedly the child wouldn't sit in her seat. Then yesterday I heard rantings about this from Neal Boortz on the radio and promptly turned the dial. (my rule of not taking child-rearing advice from people with fewer children than I had been violated) His take was that this girl was acting badly because her parents didn't whack her on the bottom. However, I have flown over 8 trans-Atlantic flights with infants and toddlers and know how difficult and frustrating it is to fly with little ones.
Children are not little robots that do exactly what they are told, especially in unknown situations (like flying). Think about how scary it must be from a 3 year old's point of view. A normal toddler wants to cuddle with Mommy, not sit in a strange seat on a crowded plane, knowing their ears are going to pop, that they won't be able to run around for a long time or play with their favorite toys.
Some suggestions for flying with small children:
Read several stories about airplanes and flying the week before the trip. At the airport and on takeoff remind him of what you read. Describe the steps the pilot must perform to get the plane to fly, to navigate, to land. Distract him from his fears by gettting him interested in the crew's job.
Bring lots of snacks that the child likes as well as asking for juice or milk (bring own sippy cup) as soon as you are seated.
Bring small and quiet new toys, wrapped, in a child's backpack to keep him occupied throughout the flight. Coloring books, etch-a-sketch, small books, magnet games, matchbox cars... I found some spinning light toys once that occupied my toddlers for over an hour on a trip. He is allowed to open one gift per hour or so.
Plan on spending all your flight time taking care of the child. This isn't the time to catch up on reading or sleeping. Your child is likely anxious and scared of all the strange sounds and sights, reassure him that you are taking care of him. You will likely have to read Scuffy the Tugboat 800 times during the flight, but will emerge at your destination with a cheerful toddler, a grateful plane-full of fellow travelers, and no ejection from your flight.