Atlas Air is a US air cargo company. Their parent company, Atlas Air Worldwide Holdings Inc., is based in Purchase, NY and also owns Polar Air Cargo. They do work for other airlines flying in a wet-lease type capacity. An explanation of their business taken from the AAWH webpage:
Atlas Air’s principal business has been providing aircraft, crew, maintenance and insurance (ACMI) services for a number the world’s leading airlines. Under an ACMI contract, clients receive a dedicated aircraft in exchange for a guaranteed minimum monthly level of operation. This model allows clients to utilize Atlas Air efficiencies in order to expand their presence in the world’s cargo markets without committing to aircraft ownership. Atlas Air also has a growing charter operations that provides airlift to commercial customers and the United States military.