Have you ever cried on a plane? I have and I've written about it more than once on this blog. As it turns out, not only am I not alone in this, it's not even uncommon.
I just read an article in The Atlantic that discusses this behavior and some of the explanations related to it. I recommend it. The article is insightful--and validating.
Why We Cry on Planes by Elijah Wolfson, The Atlantic