stow away?
Yes, I agree with an earlier post, the only way I can see this happening is if you are onboard as a crew member from the airline (Pilot, Engineer, Mechanic, Load Master), or even as a "jumpseating" flight crew member from another airline (all of which you are apparently not) approved government official (FAA, Secret Service etc) , or you would have to be a required courier escorting a specific cargo (military hardware, priceless art, racehorses, etc). Otherwise you could charter the plane yourself (big bucks) where one sometimes gets interesting passengers. I once flew a one legged Dane with his Rottweiler and 3000 fur mink as he relocated his mink farm from Denmark to Newfoundland. He chartered the plane, and he was the required escort for his live animals.
Other than that, it isn't like in the old days, you can't just hitch a ride, as it was correctly pointed out that especially in the USA, you could not get past security. But I understand that you can still book passage on a ship freighter. That would be interesting too, and someday if I need weeks of no distractions, and the peace and quiet to write a book, I'll do that. But not if that ship sails anywhere near Somalia!