 Denver International Airport ( IATA : DEN , ICAO : KDEN ) , commonly known as DIA , serves as the primary airport for a large region surrounding Denver . DIA is located 18 @.@ 6 miles ( 30 km ) east @-@ northeast of the Colorado State Capitol . DIA is the tenth busiest airport in the world and ranks fourth in the United States , with 51 @,@ 245 @,@ 334 passengers passing through it in 2008 . It covers more than 53 square miles ( 137 @.@ 3 km2 ) , making it the largest airport by land area in the United States and larger than the island of Manhattan . Denver serves as a major hub for United Airlines , is the headquarters for Frontier Airlines , and is the fastest @-@ growing focus city for Southwest Airlines . 
