United Airlines is getting tough on passengers with oversized carry-on bags.

The Chicago-based airline has installed new bag-sizers at most airports. It also emailed its frequent fliers, reminding them of its rules on carry-on size. United says there is no change in policy — just a campaign to improve passenger awareness.

Some of United’s new sizers are located prior to security checkpoints. As of Saturday, employees contracted by the airline are sending passengers whose bag exceeds the dimensions for carry-ons back to the ticket counter, where they check the bag and pay a $25 fee. Airlines have traditionally asked people with oversized bags to check them at the gate, but waived the $25 fee at that point.

Some travelers are suggesting this is part of a larger attempt by United to collect more fees. The airline says it’s simply trying to speed up the boarding process.

The size limits on carry-on bags have been in place for years, but airlines have been inconsistent in enforcing them. Passengers are allowed one carry-on bag to fit in the overhead bin that needs to be 9 inches by 14 inches by 22 inches or smaller. They can also bring along one personal item such as a purse or laptop bag that fits under the seat in front of them.

The process of getting on a plane dramatically changed in 2008 when U.S. airlines started charging $25 to check a suitcase. To avoid the fee, more passengers started bringing their suitcases — many of them overstuffed — into the airplane cabin. Suddenly there wasn’t enough room in the overhead bins for everyone’s bag.

Although more United passengers may end up paying a $25 fee, having fewer bags on board could also have its benefits.

“I’ve been whacked more times than I can count by people loaded down with their life’s worldly possessions,” says Brian Kelly, an industry watcher who writes about flying trends at ThePointsGuy.com.

(AP)