ABSTRACT
In the commerce of air transportation, no single development has had wider signifi cance than the introduction of two-way voice communications in the mid-1930s. Th is innovation made it possible for controllers and pilots to coordinate their activities day or night regardless of the weather. It also launched an acculturation process and lexicon that became the foundation for modern air-traffi c control (ATC) operations. Now, every day in the National Airspace System (NAS), millions of radio transmissions are made between controllers and pilots to coordinate fl ight clearances, weather reports, and information on every conceivable equipment, traffi c, or environmental factor that may aff ect operations. Th e end result of this communication is a shared understanding of the situation and mutual comprehension of one another’s actions and intentions.
