Two related, but off-topic anecdotes.

I don't know about planes or high altitude riding, but as pucci says, heat can do it. I used to drive a station wagon and often left my bike in the cargo area. Twice during the summer, I came out from work to find that I had one or two flat tires. The bike shop guy told me it was from heat... deflate the tires if you're going to leave the bike in the car during the summer.

Story 2, further off topic: I had a friend that was out in California, driving up... whatisit, Bishops Valley? On the Nevada side of the Sierras, anyway. Drove up Tioga Pass to Yosemite, and on the way heard a big POP!! Couldn't figure out what it was until that night when the found the exploded bag of potato chips. (I know, I know. Celllophane bags aren't tires, I just thought it was funny.)