Philippine 1928 L.O.F. overprints on 2c Rizal (three #C18), 4c McKinley (five #C19) & 16c Dewey (#C24) tied by diminutive air plane cancels on U.S. Army Air Service Experimental Flight #30b (old #20gg) from San Jose, 11-18-28, to Manila, and on to Switzerland with 12-17 receiver. Registered with all appropriate etiquettes including Manila registry exchange label on back. Also with Special Flight cachet type 21 dtd 11-28 in purple and 4-line servive cachet type 4 in green. Very Scarce experimental flight, Only 13 letters carried! An Attractive & Very Fine cover with slight foxing.