Frontier Airlines is a major American ultra low-cost airline headquartered in Denver, Colorado. It operates flights to over 100 destinations throughout the United States and 31 international destinations, and employs more than 3,000 staff. The carrier is a subsidiary and operating brand of Indigo Partners, LLC, and maintains a hub at Denver International Airport with numerous focus cities across the US and Puerto Rico.

A low-cost carrier (LCC) or low-cost airline, also called no-frills, budget or discount carrier or airline, is an airline that is operated with an emphasis on minimizing operating costs. It sacrifices certain traditional airline luxuries, for cheaper fares. To make up for revenue lost in decreased ticket prices, the airline may charge extra fees such as for carry-on baggage. As of April 2020, the world's largest low-cost carrier is Southwest Airlines, which operates primarily in the United States, as well as in some surrounding areas.