When traveling in North America which carry-on you need is simple; a domestic carry-on (22’’-14’’-9’’) is accepted by all the major carriers. However, things get murkier when traveling overseas. While many luggage makers sell international carry-ons there are no set carry-on sizes that each airline takes and very few rules regulating sizes overseas.
If you are flying direct overseas or using connecting flights, things nowadays are fairly simple. IATA Resolution 302 states that whoever the marketing carrier is (the company that you booked your flight from) their baggage rules must apply to all legs of your trip. So if your ticket says United, American, or any other major US carrier then your domestic carry-on will suffice. If you are booked on a major international carrier, refer to their website and follow their guidelines.
Things get murkier if you have multiple legs of your trip booked separately, especially if you will be using overseas regional jets. Each regional airline overseas has a different standard for what qualifies for a carry-on and most have weight restrictions that really limit what you can pack in your suitcase. Please make note of any weight restrictions before packing and I recommend always having a luggage scale.
So if you are going be using regional overseas carriers you might have to rethink how you pack. My best recommendation is to consider not using a carry-on at all. For example, if you are going for several weeks and using several regional carriers, then a 25’’-26’’ suitcase plus a backpack, tote, or wheeled tote might be a perfect solution for you. You will have to check a bag either way so a smaller personal bag might be all you need to keep emergency items in.
For student’s studying overseas I really like convertible backpacks, especially ones without wheels. They can be carried either like a backpack or a shoulder bag and have cinches that allow the bag to be adjusted to your specific needs and they usually weigh less then wheeled bags. My current favorite is the Lite-Gear Travel Pack. It can hold as much as a conventional carry-on and only weighs two pounds.
Finally, as always, less is more when it comes to packing for your overseas trip. Consider taking less then you usually pack, especially when it comes to shoes and accessories. You will be doing a lot of walking so plan on taking your most comfortable and easy to use clothing and shoes. The good news is planning for your trip in advance will help avoid nasty surprises on your trip, and that is something we all can appreciate.