Issued in 1966, this Mexican airmail stamp commemorates the IX Congress of the Unión Postal de las Américas y España (UPAE). The design, by A. Brisha, features a stylized red flag inscribed with the congress title and year, symbolizing cooperation among Spanish-speaking postal administrations. Below it appears the classic post horn — an enduring emblem of international postal communication — rendered in black. The 80-centavo denomination marks its use for airmail correspondence, and the clean typography “AEREO MEXICO” emphasizes the national contribution to hemispheric postal unity.