Other than children on planes, carry-on bags might be the most regularly contentious part of airline travel. Most travelers have been on both sides of the issue because sometimes they don’t have much to take on a plane, and sometimes they do.

It’s not just the fees for checked baggage, either. Personally, I have elite status on United, but like many others, sometimes I just don’t want to risk waiting 30 minutes or longer for a bag. (During the last year, I’ve had checked luggage appear almost as soon as I make it to the luggage carousel, and at times I’ve waited over an hour. Clients and friends report the same inconsistency.)

On the other hand, there’s nothing that slows up boarding like people with carry-on issues.

United Airlines is now making a push to do something about the carry-on overload. The airline will tell workers at security checkpoint entrances to eyeball passengers for over-sized bags. Plus, it is putting out bag-sizing boxes at airports before security. They’ve also sent a reminder email to Mileage Plus members.

Passengers whose bags are judged to be too big may be sent back to check their bags, and unlike those who gate-check, will have to pay the bag fee if their bag is too big unless they have elite status.

United thinks this will speed up the boarding process. In theory, it will and, of course, earn them more revenue. They may be right. But, there are a few caveats.

First, while the new policy may speed up boarding, it is likely to slow down the security line, especially while passengers discuss the issue. If the bag in question is over-sized because it is stuffed, travelers may try to re-arrange things into their second carry-on and/or pockets. (I’ve seen people actually start putting on layers of clothes from their bags when stopped for this reason in the past.)

Second, anyone who has one or two must-check bags still has extra impetus to try to sneak an extra bag through. I’m guessing anyone who returns to the line for a second time isn’t likely to be assessed the higher second or third bag fee.

Third, it doesn’t address the infuriating problem of passengers with seats towards the middle or back of the plane using priority boarding to stash their carry-ons in the front rows, thereby making it impossible for people in those seats to stow their own bags. This then starts the whole swimming upstream process as those in the front rows put bags further back and have to make their way back to their own seats. A process repeated upon arrival.

Fourth, there’s still the issue of numbers of bags, especially with post-security purchases. Now, most people don’t buy much — perhaps reading material and/or food. But I’ve been in boarding lines where folks in front look like they’ve done half their Christmas shopping at the airport. And gate agents are incredibly inconsistent on this. Some will stop passengers over a third bag containing a couple pounds of candy, others turn a blind eye. In Dulles last year, I was behind a man with FOUR bags, all decent sized, and he wasn’t even questioned.

In general, I’m personally a fan of a crackdown. But I may need to remind myself of this on the next occasion I have to loosen my expandable carry-on a little. What do you think, Consumer Traveler readers?