The Army Airways Communication System (AACS) played an important part in the war effort. For the most part unsung heros, men of the AACS built "Highways In The Sky" that provided routes for aircraft to follow. These highways consisted of radio beacons that gave aircraft a course to follow over their route. These highways, both stateside and overseas, were a tremendous help for aircraft to get from point to point and also aided bombers to find their way home after missions.
Some of the service AACS provided:
I've only recently started research into the worldwide AACS, which was formed in 1938, and hope to provide much more information and credit to the men and women who provided these services to the Air Corp and Navy fliers in World War II and following. Many of the air traffic services or procedures they pioneered in WWII are still in use today in the armed forces, as well as in the FAA, although much modernized.