To test the effect of airport security x-rays on film, two rolls of Fuji Provia 100f were taken from the same emulsion batch. On was exposed to x-rays seven times on the way to the location, and another seven times an the way back. Both rolls were used to photograph the same scene on location. Upon the completion of the trip both rolls were used to photograph a simple color chart. While the scanned images that appear on a computer monitor may show some very slight differences, close scrutiny of the original chromes on a light table using an 8x loupe revealed no difference between the image pairs.

This is not to suggest one should let one's film pass through the airport x-ray machines when one travels. On the contrary, I recommend insisting on a hand-check whenever possible. However, if your film does get x-rayed occasionally, it is probably nothing to worry about. Be sure to put the film through all by itself, as some x-ray machines step up the power when they encounter an opaque object.