Airmail stamps are popular among US collectors. Some of that is because of the fascination surrounding Scott #C3a, the inverted Jenny. How many collectors realize that airmail stamps were created for different purposes?
The first airmail service in the US was on May 15, 1918 between Washington DC, Philadelphia and New York. In 1924, the USPOD set up three airmail zones: New York to Chicago, Chicago to Cheyenne, and Cheyenne to San Francisco. Over the years, airmail service was expanded to other US cities. The USPOD carried some of the mail by air. Contract airmail (C.A.M.) flights began on Feb 15, 1926 where private carriers would fly the mail under contract for the USPOD.
In some ways, airmail is like the Priority Mail rate of today. Years ago, letters were transported by surface mail at normal first class mail rates. If you wanted faster delivery, you sent it by airmail and you paid additional postage. Gradually over the years, the USPOD moved more and more mail by air. On Oct 11, 1975, the USPS abolished the domestic airmail service. There was no need for it any more. By 1975, most of the mail was moving by air anyway. By 1975, airmail stamps guaranteed that your letter was going by airmail. However, a lot of first class mail was being transported by air too because the USPS was getting away from transporting mail by surface, especially between cities that were far apart. Airmail was faster and cheaper.
The first six airmail stamps, Scott #C1-C6 were issued for airmail service between a very limited number of cities.
The next 82 issues, Scott #C7-C88, were issued for a variety of domestic and international airmail rates.
Scott #C89 and later issues were issued for international airmail rates. At one time, there were separate postage rates for surface versus airmail delivery of letters to foreign countries. Today, airmail is the only postage rate.
The Scott catalog lumps all airmail stamps into a single category under the “C” designation. However, the airmail stamps were issued for a variety of different reasons. Now you know the gist of why the different airmail stamps were issued.