The Nine-cent Prexie
Air, Surface, Air Postcard
Postcards did not have their own foreign airmail rates until June 1, 1954. A postcard sent using air in the United States, surface transportation abroad, and then air to the destination should have been charged three cents for air transport, three cents for surface, and three cents for air.
This postcard was mailed in Hawaii in January of 1939 with the stipulation that it go by air to Germany. Full airmail transport would have cost twenty cents to the mainland, and there was no airmail from there to Europe until April 28. One would expect the total charge to have been three cents to the mainland by surface, three cents surcharge to the east coast departure point by air, three cents to Europe by surface, and three more for air transport inside Europe. Apparently the card was not paid to go by air to New York, or perhaps not within Europe, though for all we can tell it may have received both services.
I have a number of other postcards using air, sea, air where the postage paid was eleven cents: three for air in the States, five for surface to Europe, and three for air within Europe. These are all from the same correspondence, and the sender may have been given erroneous information the first time they used this combination and just continued to use the letter rate for the surface portion. Nine cents would appear to be correct. However, I only have been able to find one example of air-sea for six cents and one other (mainland) air-sea-air for nine cents.