"On Schedule" joke

A mother and her son were flying Qantas from Perth to Sydney (in seats 24E and 24F).

The son, who had been looking out the window, turned to his mother and said,"Why don't big planes have baby planes?"

The mother, who couldn't think of an answer, told her son to ask the flight attendant.

So, the little boy asked the flight attendant, "If big dogs have baby dogs and big cats have baby cats, why don't big planes have baby planes?"

The flight attendant asked, "Did your mother tell you to ask me that?"

The boy said that she had.

With a clever grin, the flight attendant said, "Tell your mother it's because Qantas always pulls out on time."