divided into concourses D and E, was built to the east of the existing terminal where once the Empfangsanlage Ost had been. With its opening in 1994, Frankfurt Airport increased its terminal capacity to 54 million passengers per year. Along with the terminal opening, a people mover system called Sky Line was established to provide a fast connection between Terminal 2 and Terminal Mitte (now renamed Terminal 1). In 1999 a second railway station, primarily for InterCityExpress long-distance trains (called Frankfurt Airport long-distance station), opened near Terminal 1 as part of the new Cologne–Frankfurt high-speed rail line. At the same time local and regional rail services were based at the existing underground station, now renamed Frankfurt Airport regional station. Closure of the Rhein-Main Air Base On 30 December 2005, the Rhein-Main Air Base in the southern part of the airport ground was closed and the US Air Force moved to Ramstein Air Base. The property was handed back to Fraport which allows the airport to use it to build a new passenger terminal. The property of the housing area for the soldiers, called Gateway Gardens, which was located north-east of the airport site, was given back to the city of Frankfurt in the same year and will be developed as a business district in the following years. The Airbus A380 and The Squaire From 2005 to 2007, a large Airbus A380 maintenance facility was built at Frankfurt Airport because Lufthansa wanted to station their future A380 aircraft fleet there. Both terminals also underwent major renovations in order to handle the A380, including the installation of a third boarding bridge at several gates. Lufthansa's first Airbus A380 went into operation in June 2010 and was named Frankfurt am Main. In 2011, a large office building called The Squaire (a blend of square and air) opened at Frankfurt Airport. It was built on top of the Airport long-distance station and is considered the largest office building in Germany with floor area. Main tenants are KPMG and two Hilton Hotels. Since 2012, the people mover "The Squaire Metro" connects the Squaire with the nine-storey parking structure. On a length of about 300 metres the so-called MiniMetro system with its two cabins can carry up to 1,300 passengers per hour. The constructor of the system was the Italian manufacturer Leitner. The fourth runway Plans to build a fourth runway at Frankfurt Airport were underway