One word: Dramamine [or other sleepytime med]

It says it is not recommended for children under 2 years without advice from your doctor. If he is 18 months, etc.. you could have talked to your doctor about such an option, found a solution to calm him during the flight, etc. I am not an advocate of just drugging every kid that is a problem, but in this situation, he was a clear and present danger to your unborn child, this was an exceptional situation, etc..