When it comes to protecting the skies, various terms come into play as synonyms for "guard air". One widely recognized term is "air defense", which refers to the measures taken to safeguard airspace from potential threats. Another synonymous phrase is "air security", emphasizing the protection of aerial domains from unauthorized entry or malicious activity. "Aerial protection" also signifies the act of keeping the airspace safe and secure. Additionally, "airspace defense" conveys the concept of actively defending and monitoring airspace against potential intrusions or attacks. These synonyms all encompass the crucial mission of protecting the skies and maintaining the integrity of the airspace.