The United Airlines Baggage Policy has an easy-to-understand policy that facilitates the planning of your journey. The majority of travelers are permitted to check in one carry-on bag and one personal item such as pocketbook or small backpack is free. The cost of checked luggage varies based on your MileagePlus level, ticket class, and destination. Economy travelers usually have to pay for the first checked bag and there are additional costs for subsequent bags or luggage that weighs more than