Cover franked with 1929 15c on 15p black AIR overprint on 'Train' issue, 1929 3c deep purple and 1927 1c olive green TAX issue (SG 230, 241 & 223) tied by large CORREO AEREO GUATEMALA cds's in red dated AUG 7 1929 with boxed 'SERVICIO POSTAL AEREO GUATEMALA C.A. PESO EN GRAMOS' marking alongside also in red. Flown on the GUATEMALA CITY - MEXICO - BROWNSVILLE first flight with MEXICO D.F. transit cds and USA arrival cds's on reverse. (Muller #13)