Marine One is the call sign of any United States Marine Corps aircraft carrying the president of the United States. It usually denotes a helicopter operated by Marine Helicopter Squadron One (HMX-1) "Nighthawks", consisting of either the large Sikorsky VH-3D Sea King or the newer, smaller VH-60N "White Hawk". Both helicopters are called "White Tops" because of their livery. Any Marine Corps aircraft carrying the vice president of the United States without the president has the call sign Marine Two.