The ratings on Chicago-based Boeing Co. are supported by its very strong position in defense and military space sectors; its position as one of two global producers of large commercial aircraft; efficient operations; and good overall financial performance, especially solid cash generation and very ample liquidity. The ratings also take into account highly competitive markets, cyclicality of the commercial airplane business, and sizable, albeit reduced, unfunded postretirement obligations. Boeing is the world's largest aerospace firm, with 2006 revenues estimated at $60 billion and a good balance of military and civil activities. The firm is one of the largest U.S. defense contractors, with diversified operations and a number of major, well-positioned programs and good profitability. In 2006, defense and space activities