Inferences
Commonly used words are larger and slightly faded in color. Less common words are smaller and darker. London, Aero Heliport, Kahuliui are some airports closest to many UFO sightings. From the figure above, we found the most commonly-mentioned airports are Sch heliport and Sunset airport. They are small airports. Sch heliport is in Nevada, Iowa, Sunset airport is in Washington DC.