Modern aircraft have become much quieter over the last two decades. The largest business jets operating at Centennial are remarkably quieter than some of the smallest aircraft using the airport. All aircraft are categorized by the amount of noise they make. The loudest aircraft are called “Stage I” and “Stage II”. Both will be banned from using Centennial Airport by 2015. “Stage III” and “Stage IV” aircraft are the quietest. Many aircraft at Centennial meet “Stage III” requirements and some even meet “Stage IV”.