First Day Cover April 28, 1938 reused as a Flight cover September 27, 1938 for the short lived semi official Areovias Nacionales Hydroplane flight of 1938. Sanabria #S1, S3, S4, S5, S6, S7 tied, for an airmail flight to Ponce, Puerto Rico. Only a few of each stamp were used on flights covers and very few were carried aboard the Kofresi flight of September 27. Typical tropical toning, soiling, bumps, nick at top etc.. Scarce to rare. (Image)

First Day Cover April 28, 1938 for the short lived semi official Areovias Nacionales flights of 1938. Sanabria #S2, tied. Only 2,000 of the 10 cent light blue were issued without surcharge. Tough to find single use FDC. Typical tropical toning and pencil markings. (Image)

First Flight First Day cover April 28, 1938 for the short lived semi official Areovias Nacionales airmail flights of 1938. This one is a FDC for Sanabria #S5, S6 tied to an airmail flight to New York. Only around 10,000 of each stamp were printed. Typical tropical toning. (Image)

First Flight cover September 27, 1938 for the short lived semi official Areovias Nacionales Hydroplane flight of 1938. Sanabria #S2, S4 tied, surcharged on envelope and stamp to 10 cents, for an airmail flight to St. Croix, V.I.. Only the 10 cent stamps were overprinted and revalued. Few covers exist. Typical tropical toning. (Image)

First Flight cover September 28, 1938 for the short lived semi official Areovias Nacionales Hydroplane flight of 1938. Sanabria #S1 x2, S3, S4-S7 tied, for an airmail flight to St. Thomas, V.I.. Only 8,000 of the 10 cent stamp were overprinted and revalued. Lightly addressed to San Juan. Typical tropical toning. (Image)

First Flight cover September 28, 1938 for the short lived semi official Areovias Nacionales Hydroplane flight of 1938. Sanabria #S1, tied, surcharged on envelope and stamp to 10 cents, for an airmail flight to St. Thomas, V.I.. Only a few of each stamp were overprinted and revalued. Typical tropical toning. (Image)