Rolls-Royce Holdings plc is a multinational public holding company that through its subsidiaries, designs, manufactures and distributes power systems. Rolls-Royce Holdings is headquartered in City of Westminster, London. It is the world’s second-largest maker of aircraft engines, and also has major businesses in the marine propulsion and energy sectors. Rolls-Royce was the world's 16th-largest defence contractor in 2011 and 2012 when measured by defence revenues. It had an announced order book of £71.6 billion as of January 2014.