An ultra-low cost carrier, also known as ultra-low cost airline or abbreviated to ULCC, is an airline that operates with a low cost business model, meaning customers get tickets at a much lower cost.

An Ultra-Low-Cost Carrier (ULCC) is an airline model that prioritizes the absolute lowest possible base fare by "unbundling" almost every service that was traditionally included in a ticket. Unlike standard Low-Cost Carriers (LCCs) like Southwest, which may offer free checked bags or snacks, a ULCC like Spirit, Frontier, or Ryanair operates on a "pay-for-everything" basis. Their business model relies on high aircraft utilization, a single type of aircraft to minimize maintenance costs, and flying into secondary, cheaper airports. When you buy a ULCC ticket, you are paying only for your seat and a small personal item (like a purse). You must pay extra for a carry-on bag, a checked bag, seat selection, boarding priority, and even water or snacks onboard. This model allows price-sensitive travelers to fly for remarkably low prices—sometimes less than the cost of a train ticket—provided they are willing to sacrifice legroom and amenities. For the airline, the goal is to make a significant portion of their revenue through these "ancillary fees," which often end up costing more than the original base fare if the traveler isn't careful.