“What I didn’t realize, because it’s never become an issue, is that American (as well as Delta and United) have fairly new carry on bag limits, including a 14-inch maximum width, and my Rimowa is 15 inches wide, as are many carry ons. Even though it’s an inch shorter than the 22-inch length limit, and an inch shorter than the official 9-inch depth limit, back to check in I went. And the line was so long, I almost missed my flight. I was then told that this is a new ‘FAA regulation’ but I doubt that’s true, since some airlines still have more generous allowances. And these size limits are fairly recent policies. In fact, United made the change on March 2, 2014.”
http://www.airfarewatchdog.com/blog/18811748/airlines-change-the-carry-on-rules/