Wouldn't it be a lovely and joyous world if airlines had consistent restrictions for the size and weight of carry-on bags? Dreams smashed. Not all airplane overhead storage is created equal. Every airline company bases their bag restrictions on the internal configurations of their fleet. Which means, in short, a bag could be carried on one flight but must be checked on another.
Luckily domestic airlines like US Airways, Delta, American, and United agree on their max size, 22 x 14 X 9 inches. Unfortunately, most wheeled luggage pushes those dimensions to the breaking point. I myself have had to gate check a bag because the wheels were just too big for the overhead compartment to close.
A few domestic airlines are more generous with their bag restrictions. Alaska Airlines allows a whopping 24 x 17 X 10 inches (so passengers can fit their parkas on board, we assume). AirTran and Southwest allow 24 by 16 by 10 inches. Unless you’re carrying bricks, carry-ons are rarely weighed.
If you’re abroad, carry a backpack or light squish-able duffel. European airlines have extremely strict carry-on dimensions. Weight is a big factor, as well. Air France and Alitalia limit carry-ons to 21 X 13 X 9 inches with a max weight of 26.4 pounds. Carry-on bags on Lufthansa, Swiss, and Turkish can be 21 X 15 X 9 inches but these airlines counterattack with a max weight of 17.6 pounds.
New seats and floatation devices often means less than eight inches of clearance for bags under the seat in front of you with a maximum width of 14 inches. The middle seat in a three seat row has even less space under the seat.
Our advice, if you know you will be heading abroad or traveling different size planes, it’s worth it to buy a light, smaller carry-on around 21 X 13 X 9 inches. A bag that size will fly almost anywhere if you don’t stuff it with heavy, unforgiving objects. Remember, overhead bins aren’t “very” pliable, so be sure to measure your carry-on before you haul it all the way to the gate, only to be forced to check it.