United Airlines does not include checked bags in its economy class cabin. This cabin is one level up from the standard, so there is limited facility available. If one is a premier member, then they can be allowed to carry checked bags with them in this cabin. Besides this, flyers flying with Economy or Economy Plus United also request to carry checked luggage along with them, by paying a fee. For more details about the different economy levels of United Airlines, check out the blog at the provided link by the AirlinesGroupTravel website.