A ballistic missile is a missile that has a ballistic trajectory over most of its flight path, regardless of whether or not it carries a weapon. Ballistic missiles are categorized according to their range – the maximum distance measured along Earth's surface from the point of launch to the point of impact of the last element of the payload. Various schemes are used by different countries to categorize the ranges of ballistic missiles. The United States divides missiles into four range classes as shown in the table below.