As the battle of the bags gets more competitive at the airports, fliers should be warned that the rules are not always as clear or as fair as they could be.
Although his bag fit in the sizer, it stuck out one inch at the top, he said. Normally the bag is still allowed because the overall size of the bag is 43 linear inches, below the airline's stated 45-inch maximum. He was forced to hoof it back to check in, and he nearly missed his flight.
"When I got on the plane, there was a woman with my exact same bag in the overhead bin," he told CNBC. "Enforcement can be very arbitrary."
Many of the major airlines limit carry-on bags to 45 linear inches: 14 inches wide by 22 inches long and 9 inches deep. Spokesmen for American, Delta and United on Friday all told CNBC they haven't changed those dimensions in years.
In March, United launched a very public campaign that it would begin better, more consistent enforcement of its existing carry-on limits. That change of enforcement has led to faster boarding of the planes, Charlie Hobart, a United spokesman said.
The request for more enforcement came at the request of fliers who had been complying with the rules all along, he said.