DO NOT EVER PUT FILM IN CHECKED BAGGAGE. Many airports are using CTX 5xxx series xray machines for checked baggage. These machines DO increase power until they can ID everything in the bag. Since they run totally unattended, they use MUCH higher xray levels than any carry on scanner. They can fog slow film in a single pass through the machine.(posted 8589 days ago)The scanners used for carry on baggage are fairly low power and do not offer increasing the power until they see what is in there. If they can't see it with xray, they look in your bag with their eyes. Also since people work close to the units, with the open ends, there is a limit to the xray levels that can be used. They CAN stop the item in the xray field to take more time to look at something, but this is still not damaging to film.
I have not heard of anyone having film fogged by even multiple passes through a carry on baggage scanner except one case in a third world country.