The $30 CardBoard McCain, bought in a shopping mall music store, sits in Seat 16F, ABC News reported.
CNN said the press put the likeness in the plane as an irreverent reference to Democratic vice presidential candidate Joseph Biden's tendency to refer to McCain as "my friend" and to tell voters a variation of a story he told in West Palm Beach, Fla., last week.
"If John McCain picked up the phone today and said, 'Joe, I need you to get in a plane and fly out to Missoula, I can't tell you why,' I'd get in a plane and I'd go," Biden said. "And I believe he'd do it for me."
Biden spokesman David Wade responded to the joke with a quip about Republican vice presidential candidate Sarah Palin.
"You realize you could've made history," Wade said. "If you'd found a cardboard cutout of Gov. Palin, that's the closest she would've been to taking tough questions from the national media since she was selected."
McCain-Palin spokesman Ben Porritt told CNN: "This is probably a great day for Joe Biden. He's never been shy about wanting to campaign on the same ticket as John McCain."