Dan,
It's been tried. Back in the early 70s a guy tried it. He froze to death in the cargo compartment of a jet airliner. Guess he didn't know that section wasn't heated during flight.
Another, a Cuban, tried stowing away in the wheel well of a jet. He made it to Miami but when the pilot lowered the landing gear over Biscayne Bay on his approach to MIA, the frozen body of the stowaway fell out into the bay. Rotten way to go.
If you try it, pack some food and go UPS ground, and do it in the spring or fall. Nicer weather.
Tom