Why Often-Overlooked Atmospheric Pressure Is Critical for Every Pilot

Altimeter settings vary wildly in mountainous terrain, so lean on a lifesaving habit.

Scott Dennstaedt, Ph.D

Friday, November 21, 2025 at 08:00 AM ET

Verified

Edited By:

Travis Tingle

There is a way to understand the crude science of sea-level pressure reduction and how high-elevation airports can throw off your flight's most critical number. [Credit: Adobe Stock]

Key Takeaways:

Atmospheric pressure is a critical, yet often underappreciated, weather element for pilots, especially in mountainous regions, as it's essential for accurately determining height above the Earth's surface.
Altimeter settings are calculated by reducing measured station pressure to a theoretical sea level pressure using a standard atmosphere model, which can lead to significant variations and deceptively high readings at high-elevation airports, even across short distances.
These calculation artifacts mean that altimeter settings can differ considerably in mountainous terrain, highlighting the importance of using the most local and current setting available.
Pilots must consistently use the altimeter setting provided by local Air Traffic Control (ATC) or Automated Surface Observing System (ASOS)/Automated Weather Observing System (AWOS) to ensure accurate altitude indications and prevent dangerous discrepancies that could compromise flight safety.

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No, this doesn’t address the anxiety you might feel while shooting an instrument approach to minimums or the intense pressure to keep your speed up after a slam-dunk vector to the final approach course into a busy airport.

In this case, I am talking about atmospheric pressure. Pressure is not something we ordinarily dwell on before or during a flight. But if you fly in a location where the mountain peaks are plentiful, then you should become better acquainted with how much the altimeter setting can truly vary in mountainous areas even when the weather is tranquil.