Why is it important to maintain a current altimeter setting?

Maintaining a current altimeter setting is crucial because atmospheric pressure is not constant. As weather conditions change, so does atmospheric pressure due to factors such as temperature, humidity, and altitude variations. If pilots and air traffic controllers do not use the correct altimeter setting, it can lead to significant altitude discrepancies among aircraft. This increases the risk of midair collisions, as aircraft may be operating at incorrect altitudes relative to each other.

Using an outdated or incorrect altimeter setting can result in an aircraft flying lower than intended or higher than the actual safe altitude, which can be particularly dangerous in areas with terrain or congested airspace. Therefore, ensuring that altimeter settings are current and accurate is vital for maintaining safe vertical separation and overall safety in the airspace system.