I can confirm MIA is still checking. Made me put my carry-on in sizer two weeks ago for first time ever. It clearly meets the published size restrictions (it is actually a 21" bag) but it was a little full that day. When I went to shove it in the sizer ever so slightly the checker got testy and insisted I could not push at all and that it had to slip in easily by itself. Name one bag that does that. So she agreed I could take a book out of side pocket and try again. This time she was satisfied with the "ease" with which it went in and gave me the purple tag. I have left the tag on and flown out of MIA 3 times since without anyone stopping me. Moral is once you get that tag, never take it off.