NEW YORK — United Airlines is getting tough on passengers with oversized carry-on bags, even sending some of them back to the ticket counter to check their luggage for a fee.

The Chicago-based airline has started a push to better enforce rules restricting the size of carry-on bags — an effort that will include instructing workers at security checkpoint entrances to eyeball passengers for bags that are too big.

In recent weeks, United has rolled out new bag-sizing boxes at most airports and sent an email to frequent fliers, reminding them of the rules.

The size limits have been in place for years, but airlines have enforced them inconsistently.

    Most Read Stories

People flying with oversized bags can have the suitcase checked for free at the gate. But those who get halted at the entrance to security must now go back to the ticket counter and pay the airline’s $25 checked-luggage fee.

Some travelers suggest the crackdown is part of a larger attempt by United to collect more fees. However, United spokesman Rahsaan Johnson said it has nothing to do with revenue.

Brian Kelly, an industry watcher who writes about flying trends, disagreed.

“This new program is primarily to drive new revenue and will likely delay the boarding process even more unless better education is provided around what is and is not acceptable.”

But, he added, having fewer bags on board could also be good for passengers.

“I’ve been whacked more times than I can count by people loaded down with their life’s worldly possessions,” Kelly said.