carry on is the only way. All X ray damage film to some degree. The reason you do not see it is it manifests as a low even fog exposure which you print through with some quality losss. Damage is cumulative. There are no x ray machines that do not damage film regardless of what people here say and what the airlines tell you.
Baggage scanners , if you get picked, put stripes of overexposure across the frame rendering it useless.
Digi is better for travel.