The Ramp Tower at Seattle-Tacoma International Airport, the 11th busiest airport in the nation, directs planes from takeoff to touchdown. The airport's 2,500 acres of land are constrained, leaving no room to grow and the airport moves more airplanes per square foot than any other in the country. This led to congestion, which resulted in a two-hour turnaround time. In 2006, the airport's second tower began ramp control. The use of artificial intelligence to alert the control tower, which can cost nearly a million dollars a month in wasted fuel and staffing.