Two Mexican exchange houses transferred money through U.S.-based banks that was used to buy aircraft for transporting more than $1 billion worth of cocaine, the Mexican government said this week. Mexican federal prosecutors said Tuesday that the two businesses-Casa de Cambio Puebla S.A. de C.V., a money service business, and Organizaci??n Mundial de Negocios, S.A. de C.V., an unlicensed currency exchange-helped move money to buy the planes in transfers involving 74 entities. Last May, U.S. authorities froze nearly $11 million in accounts held by Casa de Cambio Puebla at Charlotte, N.C.-based Wachovia Bank, according to court documents filed in June...