The x-ray machines for carry on stuff isn't powerful enough to fog your film. If it is ISO 800 or above, you will probobly be granted a hand check if you so request. If you put your film through in a lead lined bag, they'll probobly just dump it in a bin, and put it back through the x-ray. It seems to be the new common theme among the TSA agents, who BTW are trained online.
If you have ISO 800+ film, you will probobly be granted a hand check.
I wouldn't mail my film simply because i don't know what the mail peeps do with stuff.
If you pack film in a lead lined checked bag, the tech will open your bag, dump your film out, and put it through the x-ray. They don't give a crap about your film.
I took 20 rolls (Reala 100, Superia 400, Ultra Color 100, and Ultra Color 400) through 14 carry on x-rays and there is no hint of fogging, even when i lighten the density 15 stops, you still do not see x-ray lines.
Like duffer says, you film doesn't stand a chance against checked bag x-rays, it's screwed, don't do it.
And continuing the what duffer said thing, a hand check is not always granted.