Children's questions whilst flying

A mother and her very young son were flying Southwest Airlines from Kansas City to Chicago.  The little boy, who had been looking out the window, turned to his mother and asked, "If big dogs have baby dogs, and big cats have baby cats, why don't big airplanes have baby airplanes?"

The mother couldn't think of an answer.  "Ask the stewardess," she told him. 
So the boy went down the aisle and asked the stewardess.   The stewardess, who was very busy at the time, smiled and said, "Did your Mom tell you to ask me?" 

The boy said, "Yes, she did."
"Well, then," she replied.  "You go and tell your mother that there are no baby airplanes because Southwest always pulls out on time.  Have your Mom explain that to you."