connect downtown Saint Paul to the airport and Mall of America. The METRO A Line opened in 2016 as Minneapolis–Saint Paul's first arterial bus rapid transit line. The A Line connects the Blue Line at 46th Street station to Rosedale Center with a connection at the Green Line Snelling Avenue station. Future METRO lines are planned that will serve Saint Paul with the B Line and E Line Line running primarily on arterial streets, and the Gold Line and Purple Line running primarily in their own right of way. Railroad Amtrak's Empire Builder between Chicago and Seattle stops twice daily in each direction at the newly renovated Saint Paul Union Depot. Ridership on the train increased about 6% from 2005 to over 505,000 in fiscal year 2007. A Minnesota Department of Transportation study found that increased daily service to Chicago should be economically viable, especially if it originates in St. Paul and does not experience delays from the rest of the western route of the Empire Builder. Saint Paul is the site of the Pig's Eye Yard, a major freight classification yard for Canadian Pacific Railway. As of 2003, the yard handled over 1,000 freight cars per day. Both Union Pacific and Burlington Northern Santa Fe run trains through the yard, though they are not classified at Pig's Eye. Burlington Northern Santa Fe operates the large Northtown Yard in Minneapolis, which handles about 600 cars per day. There are several other small yards located around the city. Airports Holman Airfield is across the river from downtown St. Paul. Lamprey Lake was there until the Army Corps of Engineers filled it with dredgings starting in the early 1920s. Northwest Airlines began initial operations from Holman in 1926. During WWII Northwest had a contract to install upgraded radar systems in B-24s, employing 5,000 at the airfield. After WWII, Holman Airfield competed with the Speedway Field for the Twin Cities' growing aviation industry and lost out in the end. Today Holman is a reliever airport run by the Metropolitan Airports Commission. It is home to Minnesota's Air National Guard and a flight training school and is tailored to local corporate aviation. There are three runways, with the Holman Field Administration Building and Riverside Hangar on the National Register of Historic Places. The historical importance of the original Northwest Airlines building was realized only after demolition commenced. For the most part St. Paul's aviation