Airports are divided into several categories. 1 Based on take-off and landing 2 Determined by the approach speed of the aircraft 3 In terms of function. 4 A geometric design is employed. 5 Based on aircraft wheel characteristics. 1 Functional classifications divide airports based on their purpose. Commercial airports serve passengers while military airports serve troops and vehicles. Security checkpoints are also located at these airports to search luggage and equipment for weapons or explosives. Governmental airports are used by local, state, and federal governments. These airports are usually found in large cities where traffic volumes are high. Public use airports are those that are neither commercial nor military. They provide free flights for recreational purposes such as training pilots or a place for amateur radio operators to practice transmissions. Private use airports are also available for private aircraft or helicopters to land. 2 Geometric classifications divide airports based on how they are laid out. Circles, squares, and triangles all qualify as geometric airports. The most common type of geometric airport is the circle because that's what happens when an airplane flies over a flat surface without obstacles. Aircraft need to fly at a certain distance from the edge of the circle to avoid crashing into it. 3 Approach classifications determine how close an aircraft can come to a destination airport before needing to make an approach.