When it comes to carry-on bags, one size definitely does NOT fit all.

Airlines seem to go to great lengths to confuse and frustrate us with baggage sizers placed right next to boarding gates.

If you follow the rules, then you know that airlines have traditionally limited acceptable carry-on bags to 22 inches in length.

But when airline gate agents tell passengers they must fit their 22-inch bags in bag sizers, guess what? They no longer fit, and have to be checked.

Bag manufacturers are scrambling to design new bags that will fit those bag sizers, but it’s not working.

A recent investigation by The Wall Street Journal revealed that each airline builds its bag sizers differently.

For example, the sizer United Airlines uses is a about an inch bigger than those used by Delta or British Airways.

So be prepared for more confusion and frustration at the gates.

If you’re asked to drop your bag into the sizer, be prepared for it suddenly NOT to fit.

For more information about carry-on luggage, check out:

• How to Fit It All In One Bag: Carry-On Packing Tips
• New Proposed Dimensions for Carry-On Luggage That Could Save Space
• What to Consider Before Buying Hard Shell or Soft Sided Luggage

Keep reading for more travel tips.