Don't you love airports and delayed flights. I was able to watch a variety of parents and children yesterday for 10 hours of delays. In the airport there were about 8 hours of delays and I watched a family with a mom, two children and two grandparents who were traveling together. They managed pretty well most of the time with each child having a bag of activities to keep them occupied. Everything worked fine until the older child (8-9 years old) decided it would be more fun to torment his younger brother (about 4 years old). The mom was tired and had given up on disciplining her sons. Grandma looked like she was staring at things to keep herself from falling asleep. Grandpa calmly bulled the older boy to his side and talked with him about what he had in his bag. He knew that distraction was the key rather than telling the children to stop. The mom mentioned that her younger son needed a nap but that because they were traveling he had not had one. Because of this he had a short fuse. His mom would have been better suited to force a quiet time with a time limit of sitting down an resting as they know there would be another two hours before a potential plane.
Another couple in their late 20's had a little 24 month old who was thrilled to be able to walk/run as she found everything interesting. Mom and dad took turns as the person watching her and allowed her to move freely (within a defined space) which let her gradually wear herself down. For the 2 year old she fell asleep as her parents were getting ready to board the plane.
Back when we traveled with our children Lisa would buy little snacks or travel toys that the children were able to unwrap every 100 miles. Over the years we would just rewrap the old toys and they were new again. The kids loved getting to unwrap them and see what they got each time. It helped them to mark time.