Mail that records the expansion of domestic airmail service in the United States also records the expansion of contract airmail routes (often called “C.A.M.”s by stamp collectors), the development of heavier-than-air craft, and the practical application of airplanes to the transportation of mail—specifically, new airmail service between cities or to new cities until deregulation on December 1, 1978.
In 1926, the United States Post Office Department contracted with private operators for mail transport by private enterprise. Ford Motor Company received the first contracts, designated as C.A.M. routes 6 and 7, and service began February 15, 1926. An Act of Congress created the service, with original routes awarded after competitive bidding. In February 1933, an interruption occurred when President Franklin D. Roosevelt ordered the Post Office Department to cancel contracts. U.S. Army planes flew the mail while new bids were sought and routes rearranged.
Many stamp collectors seek specific contract routes, specific cities and regions, specific airlines, and time eras. Pictorial cachet and cancel varieties add interest to the covers.
To read more about C.A.M. mail, see:
Robert E. Haring and Perham C. Nahl, eds., “United States Official First Flights under Contract or as Designated by the Civil Aeronautics Board (C.A.Ms.), Routes 1 through 299” in American Air Mail Catalogue: A Reference Listing of the Airposts of the World, 5th edition, volumes 2 and 3 (N.J.: American Air Mail Society, 1977).