A carry-on bag should be 10 x 16 x 24 inches. If your bag is bigger than these dimensions, you should check it at the ticket counter. If it is larger than the dimensions, you will have to pick it at the baggage claim. Carry-on items are limited to one small bag, a big one, and a personal item. The personal items have to fit in the space under the seat, which is 18.5 x 8.5 x 13.5 inches.