Is one allowed to fly on a plane to go on vacation on the day of his/her mother’s Yartzeit especially if the son of the mother will miss saying some Kaddish?
A person is allowed to fly and go on vacation on the yartziet of a parent. Regarding the fact that you wil be missing kaddish, that is already more of a personal decision. On one hand your mothers neshoma gains tremendousely from your saying kaddish. On the other hand though you are saaying some of the kadashim, and there are other things that a child can do for thier parents neshoma, such as learning mishnayos, having others say kaddish and giving tzedakah l’iluy nishmasa.