A young boy is on an airplane with his mother. He asks her a question.

"If big dogs have baby dogs, and big cats have baby cats, then why don't big planes have baby planes?"

The mum smiles and tells her son to ask the flight attendant. So he does just that.

The flight attendant asks the boy if his mum told him to ask her, to which the boy replies: "Yes".

"Well that's because Southwest Airlines pulls out on time," the flight attendant explains.