Before entering the Altimeter Setting Region, what is the primary action a pilot should take?

The primary action a pilot should take before entering the Altimeter Setting Region is to obtain the current altimeter setting. This is essential because the altimeter setting is used to calibrate the aircraft's altimeter, ensuring that altitude readings are accurate relative to the local air pressure. Accurate altitude readings are vital for safe vertical separation from other aircraft, especially when operating in busy airspace or during approach and landing.

In the Altimeter Setting Region, local pressure can differ significantly from the standard pressure, which is set at 29.92 inHg (1013.25 hPa). By obtaining the current altimeter setting from air traffic control (ATC) or directly from weather stations, pilots can make the necessary adjustments to their altimeters, thereby preventing altitude miscalculations that could result in dangerous flight situations.

The other options involve actions that may not be immediately relevant to ensuring proper altitude reporting in the region. For example, notifying ATC about altitude changes is part of maintaining communication and safety in the airspace but is secondary to having the correct altimeter setting. Changing to the standard pressure setting or adjusting to a regional standard pressure may be necessary, but both depend on first knowing the current local setting. Hence, obtaining the current altimeter setting is