The carry-on suitcase is very popular for traveling, but there is a slight size difference between international carry-ons and domestic carry-ons. Most airlines let you have a carry-on for free so it's a good way to avoid baggage fees. I recently got back from a 2-week trip around Europe (London, Paris, and Amsterdam). While it was definitely the time of my life, Europe is EXPENSIVE as hell! So to save a little money, I decided I was only going to take a personal item and a carry-on suitcase because baggage fees add up, friend.