What is the significance of continental air transportation and non-continental air transportation?

TSA changed the definition of stopover to make a distinction between domestic and foreign travel, and to recognize that non-continental U.S. air transportation (outside the contiguous 48 states) is more like foreign air transportation. Stopover means a break in travel of more than: four hours for continental interstate and intrastate air transportation; twelve hours for non-continental interstate and intrastate air transportation as well as foreign air transportation.