"If God wanted us to fly, He would have given us tickets"

The quote is a humorous method of saying that people were not suggested to fly naturally. It recommends that if flying was indicated to be a part of human existence, God would have provided the essential methods (in this case, tickets). It is a play on the concept that tickets are needed for flight, indicating that humans were not geared up or meant to require to the skies without the help of technology.