Cover with manuscript 'Correspondencia enviada en el Trimotor' at top franked with 1929 3c deep purple and 1c olive green TAX issue (SG 230 & 223) tied by large CORREO AEREO GUATEMALA cds in magenta dated in error 29 ABR 1929 (it should have been the 28th). Flown on the GUATEMALA CITY - MEXICO first flight by Pickwick Airways without any cachets. SERVICIO AEREO MEXICO D.F. arrival cds on reverse dated 28 ABR 1929. Cover a little worn along top & right hand edges with vertical crease and small puncture mark well away from stamps & markings. A very rare flight. (Muller #11 rated 2500pts, Goodman #AM13)