Which of the following is NOT one of the three main types of air traffic control?

The correct answer is ground control, as it is often considered a subcategory within the broader category of tower control. The three main types of air traffic control typically refer to tower control, approach control, and en-route control.

Tower control focuses on managing takeoffs and landings at airports, ensuring safe and efficient movement of aircraft on runways and taxiways. Approach control handles aircraft as they near an airport, managing their descent and ensuring safe spacing during the approach phase. En-route control is responsible for managing air traffic at cruising altitudes between airports, guiding aircraft on their flight paths.

Ground control, while essential for airport operations, is a specific aspect of tower operations concerned with vehicle movement on the ground rather than a primary category of air traffic control.