Flying TWA

A mother and her son were flying TWA from Kansas to Chicago. The son (who had been looking out the window) turned to his mother and said, "If big dogs have baby dogs and big cats have baby cats, why don't big planes have baby planes?"

The mother (who couldn't think of an answer) told her son to ask the stewardess. So the boy asked the stewardess, "If big dogs have baby dogs and big cats have baby cats, why don't big planes have baby planes?"

The stewardess asked, "Did your mother tell you to ask me?" He said that she had.
So she said, "Tell your mother that TWA always pulls out on time."