What is the required altimeter setting for aircraft in all low-level airspace within the Altimeter Setting Region?

In the Altimeter Setting Region, the required altimeter setting for aircraft operating in low-level airspace is the nearest station altimeter setting. This is important because it ensures that all aircraft in that sector are using the same local atmospheric pressure for altitude reporting and navigation. The use of the nearest station setting helps to maintain safe altitude separation and enables pilots to accurately determine their altitude relative to terrain and other aircraft.

Unlike a flight level altimeter setting, which is typically used at higher altitudes (above FL180) and standardized to 29.92 inches of mercury, the nearest station altimeter setting reflects the actual atmospheric pressure at the airport or nearby weather station and helps to enhance situational awareness for pilots at lower altitudes. This localized information is crucial for safe flight operations in busy airspaces where elevations may vary significantly.