Well, this is kind of a sneaky way for airlines to make air travelers check their bags – and a sneaky way for at least one airline to squeeze more bucks out of bag check fees.

Earlier this month Continental Airlines announced that it would not only charge coach travelers $25 to check a second piece of luggage, it would also begin charging $15 for the first checked bag.

Continental isn’t the first airline to do this – American, United, Delta, and Northwest Airlines are among the other airlines that have also cut the size of acceptable carry-ons in the past few months.

A few linear inches may not seem like a big deal when it comes to luggage. But if push comes to shove – and it often does these days with passengers jostling for overhead space on planes – it can make the difference between snagging that bin and getting your bag gate-checked – for a fee.

So get out your tape measure and make sure your carry-on fits the new – smaller – guidelines.