Tampa, Florida -- United Airlines is cracking down on oversized carry-ons. The company says they'll catch you and it'll cost you if you try to get by with a larger bag.
Customer Danny White says, "People who do it aren't paying attention to the signs. Like any other rule, you should probably follow it."
But a United Airlines spokesperson says customers complained that too many people aren't following it.
Another traveler says, "You see people with a lot. The companies say they put a restriction but evidently don't enforce it."
United Airlines alerted customers via e-mail, put out extra sizers, and sent out an internal memo to employees to be on the lookout.
Most airlines say the carry-on bag has to fit in the sizer without being forced and can't exceed the overall dimensions: length + width + height.
Like American Airlines, United charges $25 for a checked bag. United and American also have slightly smaller requirements (9x14x22) than Jetblue or Southwest for example (10x16x24).
Some people say it's best to self-regulate and buy a small carry-on, just to make sure it'll fit.