There's also the plane ride itself to consider; at 36000 ft, there's quite a lot of radiation bouncing around, e.g.,
www.ratical.org/radiation/CNR/RMP/planes+xrays.html
Here's Kodak's take:
www.kodak.com/global/en/service/tib/tib5201.shtml
Last December, I went to Morocco. The film I brought (x30 Fuji 400H) faced four possible x-ray scans: once at JFK, once in Madrid (transit), once in Casablanca (return), and once more in Madrid.
I divided my film in two zip lock bags that fit inside two Hakuba P-1600 X-ray bags. I approached security personnel with the film in zip lock bags and requested a hand inspection. If denied, I put the zip lock bags in the x-ray bags for scanning.
At JFK, I received a hand inspection no problem.
In Madrid, I did not receive a hand inspection; however, since I had doubled up the x-ray bags, the scanner only produced an image a black block when it went through. (I was able to see the scanner monitor.) So in addition to having the film scanned, I then got a hand inspection. Meh.
In Casablanca, I was surprised with two security checks with x-ray scanning. For the first (a large, scary x-ray machine), I was denied a hand inspection, so it went through in the x-ray bags (yikes). At the second security check just after customs, I received a hand inspection.
Back in Madrid, same story. No hand inspection, went through, they couldn't see anything, and it was hand inspected.
Total times film was x-rayed: 3. Rolls with fogged images: 0. The film could have been x-rayed up to 5 times. While it was a hassle, I'm glad I took the precaution.