Actually, a friend of mine who is a medical doctor says that the cabin pressure causes many babies to cry since their ears or more sensitive than young children's, adolescents' and adults. This site also provides some more information on the topic:
http://www.mayoclinic.com/health/air-travel-with-infant/HQ00197
When I took the baby back to Trini, she was only 3 mths old. Take off and landing, baby had the boob in she mouth. Got a trick when you take 2 cups and put paper towel in it with warm water, put the cups over the ears of the baby. Works everytime