Which type of frequency is used predominantly in long-distance air traffic communication?

High Frequency (HF) is predominantly used for long-distance air traffic communication because it can reflect off the ionosphere, allowing radio waves to travel over vast distances. This capability is essential for communication between aircraft and air traffic control when they are far from ground stations, particularly over oceans or remote areas where VHF coverage may be inadequate.

HF frequencies typically range from 3 to 30 MHz and are well-suited for long-range communication, especially in the aviation industry. They enable voice and data communication even when aircraft are beyond line-of-sight. This is crucial for ensuring safety and coordination in the airspace, as air traffic controllers need to maintain contact with flights traveling through remote regions.

In contrast, Medium Frequency (MF), Very High Frequency (VHF), and Ultra High Frequency (UHF) are more commonly utilized for shorter-range communications. VHF is primarily used for communication within line-of-sight and is effective for ground to air communication, while UHF is generally reserved for military use and certain radar applications. Thus, HF is clearly the best choice for long-distance air traffic communications.