"I"ll do my crying in the rain.." - there's another place where you can do it without anyone noticing or batting an eyelid - at the airport, or on the flight. People will just think you are crying because you are going away from a place you love so much, you are going to miss the people you love.
You could be crying for a stupid mistake you made years ago in your life, or because your brother went and lost the entire set of Amar Chitra Katha which literally laid the foundation for your ethics, or because you never had that elephant ride which all the other kids had because you were too painfully shy to ask and no one bothered to ask you either. You could remember any of these and cry it all out without restraining yourself and no one will find it strange.
At an airport you are standing at the brink of parting and sorrow, you are in that intermediate space before you are shuttled into painful decisive this-is-it finality at breathtaking speed inside a narrow metal container. You are allowed to cry here.