What is allowed in carry on baggage Southwest Airlines? Passengers are permitted one carry-on bag and one personal item like a backpack or purse. The carry-on must not exceed 10 x 16 x 24 inches. Items like electronics, food, toiletries (under 3.4 oz), and books are allowed. Sharp objects, liquids over the limit, and flammable items are prohibited for safety reasons. Always check the latest guidelines for updates.