I heard that everything that you read on the Internet is true. While you may have heard something, that doesn't make it fact.
This particular assertion was originated by someone who should know a bit better; that doesn't make it a fact, either. The assertion was made in a presentation that keeps circulating around the Web via YouTube and other mechanisms and says that gamma rays kill pixels on sensors, and that gamma rays are so prevalent at the heights that planes fly that taking your camera along with you on a plane trip will damage your camera. Common sense would tell you that this assertion can't be true, as digital cameras fly on planes all the time, yet you don't hear people complaining every day about dead cameras. Mine have flown over 800,000 miles in the digital decade. Heck, many of the big Airbus planes have digital cameras mounted on the tail fin and pipe that image into the entertainment system.
Or try this: NASA flies unmodified Nikon DSLRs to the International Space Station and back. Yes, NASA does have cameras that develop some pixel problems, but you're not flying into space nor are the NASA cameras usually being damaged on a single trip. So chill. The likelihood of your camera being damaged significantly by flying with it is low. So low as to be impossible to measure accurately.