Let's all quit arguing, and study this:
http://www.kodak.com/global/en/servi...01.shtml#SEC47
As others have reported, and as I have reported in other threads, I've had no damage from airport X-rays. Like the OP, my film was X-Rayed seven times during a European trip. Three of the X-rays were done in Paris, at Charles De Gaulle airport; one when departing Helsinki; twice in Atlanta; and, I think, once in St. Louis. Films included Tri-X; Ilford 400 Delta and 100 Delta; and some Plus-X. No damage. No damage going through X-Ray in Mexico City, either.
For one of the Paris X-rays, I simply laid the film out in one of the trays, separate from everything else. The attendant gave me a questioning look. I explained that my bag was so full of stuff that they would be running it back and forth through the machine, trying to figure out what all that stuff was. By laying it out separately, they knew what they were looking at, and for, so it went through in one quick pass. Others may wish to try this!
On another trip I absent-mindedly let a roll of Delta 3200 go through on both the outgoing and return trips. No problems.
There is a post above, concerning the X-raying of Neopan 1600 (does anyone have any left? I have only 2 rolls). Neopan 1600 is really only about 640 to 800, so it does OK at airports that promise no damage under 1000. This is from my experience, not theoretical. That said, I prefer not to travel with films faster than 400. No sense tempting fate.
As in the Kodak information, my lead bag did trigger an inspection on one trip. Not a problem, just something to be aware of. It would be better to simply request hand inspection in USA airports. I've never been refused. I did not, by the way, use a lead bag for the European trip. No sense in carrying the extra weight if it's not going to do that much good. But-again, as per Kodak-damage can happen. See their examples; and if possible, as kodak says, try to avoid more than 5 X-rays. I don't see how the 300, claimed above, can be possible without some fogging!