On this day in 1920, the first ever flight using a “radio compass” was performed in Virginia.
It’s destination? A ship 100 miles off shore. Using only an AM radio station on the ship and a directional antenna on the aircraft, the pilot was able to fly directly to the Navy Ship.
Since then ADF has been refined and in some countries replaced. However it it still one of the primary form of navigation in countries like Canada, Australia, and other parts of the world with large vast distances.
Wired has more information about the early uses of ADF.