Hartsfield–Jackson Atlanta International Airport now the airport's second largest carrier. In May 2001 construction of an over fifth runway (10–28) began. It was completed at a cost of $1.28 billion and opened on May 27, 2006. It bridges Interstate 285 (the Perimeter) on the airport's south side, making Hartsfield–Jackson the nation's only civil airport to have a runway above an interstate (although Runway 17R/35L at Stapleton International Airport in Denver, Colorado crossed Interstate 70 until that airport closed in 1995). The massive project, which involved putting fill dirt eleven stories high in some places, destroyed some surrounding neighborhoods and dramatically changed the scenery of
Pittsburgh International Airport from the rest of the airport. While US Airways made immense cuts in service during the early 21st century, other carriers began to play a more dominant role at PIT. The airport's operator, the Allegheny County Airport Authority, has attempted to attract new service to the airport, particularly low-cost and international carriers. AirTran Airways, which had trouble competing in Pittsburgh after beginning service in 2000, was able to expand Pittsburgh offerings after the US Airways cuts. In 2003, USA3000 Airlines began service to Florida and subsequently expanded to include international destinations in the Caribbean. Southwest Airlines began service to Pittsburgh