Most have based it on this article from the Los Angeles Times.
One problem. The article is wrong.
The airlines have not downsized. They’re just cracking down.
United and Delta always had a carry on maximum of 22 x 14 x 9. Only now they are getting strict on that as well as the size of personal items.
American’s prior rule was a total of 45 linear inches. Now they’ve defined it to 22 x 14 x 9.
The article mentions that American went from a width of 15″ to 14″. Not technically true.
What they are basing that on is a posting by George Hobica of Airfarewatchdog. He mentioned on a recent trip he was forced to check his rolling bag that measured 15″–something he’s never had to do before. He’s also never been stopped before to have his bag measured.
Rather than saying the airlines are downsizing their carry-on limits, it would have been correct to say the airlines are now enforcing their carry-on limits.
Well, at least in theory. It’s still up to the gate agents whether or not they want to enforce the rules.
By the way, if you think the airlines are doing this so true one bag travelers will have space in the overhead, think again. They’re doing this so they can force more people to check bags. And a checked bag means additional checked bag fees.