What is the minimum altimeter setting allowed for departure?

The minimum altimeter setting allowed for departure is 28.00 inches of mercury. This limit is established to ensure safe flight operations, as it helps to maintain proper altitude awareness and separation from terrain and obstacles during departure. Using an altimeter setting below this minimum could potentially lead to inaccurate readings, increasing the risk of flying at altitudes that do not conform to the route and airspace requirements.

Establishing a standard minimum setting also aligns with regulatory requirements for operations in different airspace environments, ensuring that pilots have a sufficient baseline to safely perform their pre-departure checks and calculations. Operating with settings lower than this could compromise safety and operational efficiency, which is why 28.00 inches of mercury is set as the threshold for departures.