United Airlines, Inc. is a major American airline headquartered at the Willis Tower in Chicago, Illinois. United operates an extensive domestic and international route network across the United States and all six inhabited continents primarily out of its eight hubs, with Chicago–O'Hare having the largest number of daily flights and Denver carrying the most passengers in 2023. Regional service is operated by independent carriers under the brand name United Express.

Denver International Airport, locally known as DIA, is an international airport in the Western United States, primarily serving metropolitan Denver, Colorado, as well as the greater Front Range Urban Corridor. At 33,531 acres, it is the largest airport in the Western Hemisphere by land area and the second largest on Earth, behind King Fahd International Airport. Runway 16R/34L, with a length of 16,000 feet, is the longest public use runway in North America and the seventh longest on Earth. The airport is 25 miles (40 km) driving distance northeast of Downtown Denver, 19 miles (31 km) farther than the former Stapleton International Airport, the facility DEN replaced: the airport is actually closer to the City of Aurora than central Denver, and many airport-related services, such as hotels, are located in Aurora.