What must be done if an altimeter setting is not available at an airport?

When an altimeter setting is not available at an airport, setting the altimeter to 29.92 inches of mercury is the appropriate action. This standard altimeter setting corresponds to sea level pressure at standard atmospheric conditions, which is necessary for accurately maintaining altitude, particularly during the critical phases of flight such as takeoff and landing.

Using the standard setting allows pilots to maintain altitude reference in the absence of local altimeter information. This procedure is crucial to ensure safety and prevent potential altitude deviations that could result from relying on outdated or incorrect altimeter information. Although it is good practice to monitor for further updates or obtain local altimeter readings as soon as possible, utilizing the standard setting provides a reliable temporary solution until more precise data can be confirmed.

Other responses do not meet standard safety protocols or could introduce a higher risk of spatial disorientation or altitude discrepancies. Thus, adhering to the standard pressure setting is the best and safest option in this scenario.