United Airlines, the nation’s third largest carrier, has begun a crackdown on passengers who drag oversized bags into the cabin.

And the airline is doing this to win points with passengers.

After all, the Chicago-based carrier was recently ranked 8th among the nation’s top ten carriers in a survey of about 24,000 people in the U.S. The survey by Satmetrix, a cloud-based software company, named  Southwest Airlines as the top-rated carrier.

The crackdown on oversized bags is an effort to address what United says is one of the biggest gripes among its passengers: The overhead bins are so overstuffed with carry-on bags that the boarding process is often bogged down as fliers try to find space for their luggage.

“We are getting feedback from customers who have the right size bags, telling us that there is not enough space in the overhead bins,” said United spokesman Charles Hobart. “This is a response to that.”

United sent messages to its MileagePlus members, reminding them that carry-on bags can be no bigger than 22 inches tall by 14 inches wide by nine inches deep. The airline also distributed new “sizers” that are installed at the terminal to measure the maximum size carry-on bag allowed.

Hobart rejected speculation that United was launching the crack-down to boost revenue by charging passenger with oversized carry-on bags a $25 fee to check their luggage.

On social media sites, the crackdown was getting mostly positive reviews among airline fliers.

“Good,” Haley Gross wrote on Facebook. “This is one change I can get behind.”

Another Facebook member, Dan Banddanman, agreed. “I wish all airlines would do this. Tired of people carrying huge, multiple bags and being rude when they can’t bring them on the plane,” he wrote.

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