The IAA employs over 700 people at six locations around Ireland and has three main functions. They are responsible for the air traffic management of Irish airspace, the safety regulation of the Civil Aviation Industry, and the oversight of Civil Aviation security in Ireland. Dublin Airport has been operating since 1940, with its first flight to Liverpool, UK. Since then, more than 400 million passengers have travelled through Dublin Airport, with the old terminal building being a listed building and partially used for daily and business passenger operations. Today, Dublin Air Traffic Controllers command almost 6000 square nautical miles of airspace. The new visual control tower is a landmark building, at 87.7m tall, it is the highest occupied structure in Ireland. It was designed as a slim, elegant, conical shaped structure by Scott Tallon Walker Architects, with BAM Ireland as the main contractor. Its height, as well as the façade has been designed to ensure Air Traffic Controllers have optimum views and clear lines of sight of both current and future runways.