When we traveled in March, there was a sign by the check in area warning that the Minneapolis-St. Paul airport has the stronger x-ray machines which might damage film *edit* in checked baggage. The sign suggested carrying film in carry-on bags.*end of edit*
A friend who traveled recently was behind someone who used one of the lead bags in her carry-on luggage. When a dark blob (the bag) showed up on the carryon bag scanner, they made her take everything out of her bag so that they could see what was inside. That is what they are supposed to do, although I have heard news reports of lead lined bags getting thru screening without question.