ULCC stands for Ultra-Low-Cost Carrier, a business model that prioritizes the absolute lowest base fare by unbundling all services. In the United States, the primary examples in 2026 are Spirit Airlines, Frontier Airlines, and Allegiant Air. These airlines charge extra for everything beyond a seat, including carry-on bags, checked bags, seat assignments, and even water on board. In Europe, the most famous ULCCs are Ryanair and Wizz Air, which are known for using secondary airports to keep costs down. In Canada, Swoop (now integrated) and Flair Airlines are the main players. Unlike "Low-Cost Carriers" (LCCs) like Southwest or JetBlue—which might offer a free bag or more legroom—ULCCs use a high-density seating configuration and a "pay-for-what-you-use" philosophy. For travelers in 2026, these airlines offer incredible value for short hops if you can travel with just a small "personal item" backpack, but the total price can quickly exceed that of a legacy carrier if you add multiple "frills" like bags and priority boarding.