Pan American World Airways provides intercontinental mail delivery service in 1939

In the late 1920s and early 1930s, traditional mail pilots were becoming obsolete as airlines took over airmail services. By 1939, Pan American Clippers had established regular transoceanic flights, marking a significant evolution in airmail. The first official overseas mail flight coincided with the 12th anniversary of Charles Lindbergh's solo Atlantic crossing, highlighting his role as a pioneer in the air postal service.

On what anniversary did the first official overseas mail flight occur, and why is it notable?

Who was Charles Lindbergh and what was his role in the history of airmail service?