The 6 Types of Altitude for Pilots
Learn indicated, true, absolute, pressure, density altitude, and flight levels in plain language for student pilots and private pilots.
Altitude sounds simple until you start flying. Then you learn that "how high are we?" can have several correct answers depending on the context.
Student pilots need to know the main types of altitude because each one is used for a different cockpit decision. Some help with traffic separation. Some help with terrain clearance. Some help with aircraft performance.
1. Indicated Altitude
Indicated altitude is what you read directly on the altimeter when it is set to the current local altimeter setting.
This is the altitude pilots use most often in normal operations below the flight levels. When ATC assigns an altitude, you fly the indicated altitude based on the correct altimeter setting.
The key habit is to set and update the altimeter properly. If the setting is wrong, the indicated altitude will be wrong too.
2. True Altitude
True altitude is the aircraft's actual height above mean sea level. Airport elevations, terrain elevations, and obstacle heights on charts are based on mean sea level.
This matters because terrain clearance is not based on what feels safe from the cockpit. It is based on the relationship between your aircraft and the terrain or obstacles around you.
On a standard day, indicated and true altitude may be close. In nonstandard temperature and pressure, they can differ.
3. Absolute Altitude
Absolute altitude is height above the ground directly below the aircraft. It is an above-ground-level number.
This is the altitude that matters visually on approach and landing. If you are 500 feet above a field, that is an absolute-altitude idea, even if your altimeter is showing a much higher MSL altitude because the airport itself sits above sea level.
Some aircraft use radio or radar altimeters to measure height above the surface, especially close to the ground.
4. Pressure Altitude
Pressure altitude is altitude above the standard pressure plane. In practical training, you get pressure altitude by setting the altimeter to 29.92 inches of mercury and reading the result, or by calculating it from field elevation and altimeter setting.
Pilots use pressure altitude for performance calculations. It is also the basis for flight levels in high-altitude operations.
For private pilot training, pressure altitude often shows up when calculating takeoff distance, climb performance, and density altitude.
5. Density Altitude
Density altitude is pressure altitude corrected for nonstandard temperature. In plain language, it tells you how the airplane "feels" the air for performance.
High density altitude means thinner air. The engine may produce less power, the propeller may be less efficient, the wings may produce less lift at a given true airspeed, and takeoff distance may increase.
Hot days, high elevations, and low pressure all push density altitude higher. A runway that feels comfortable on a cool morning can become more demanding on a hot afternoon.
Density altitude is not just a written-test topic. It affects real go/no-go decisions.
6. Flight Levels
Flight levels are pressure altitudes expressed in hundreds of feet. For example, FL180 means 18,000 feet using the standard altimeter setting.
In the United States, flight levels are used in Class A airspace beginning at 18,000 feet MSL. Pilots in that airspace use the standard setting so all aircraft are referencing the same pressure level for vertical separation.
Rules vary internationally, so pilots flying outside the United States must understand local transition altitude and transition level procedures.
Transition Altitude and Transition Level
Transition altitude is where pilots change from local altimeter settings to the standard setting when climbing. Transition level is where pilots change back from standard to local settings when descending.
In U.S. training, the common reference is 18,000 feet for the transition to flight levels. Other countries may use different values. That is why you should not assume the U.S. system applies everywhere.
A Simple Way to Remember Them
Indicated is what the altimeter shows.
True is height above sea level.
Absolute is height above the ground.
Pressure is based on standard pressure.
Density is pressure altitude adjusted for temperature.
Flight level is pressure altitude used for high-altitude separation.
Altitude language can feel technical at first, but each term answers a practical question. What do I fly? What clears terrain? What will the airplane perform like? What reference is ATC using? Learn those questions, and the altitude types start to make sense.
Related Reading
Official References
Need help applying this to your training?
Use this guide as a starting point, then bring the confusing parts to a focused ground lesson. Diego works with Louisville-area and remote students on FAA knowledge, oral-prep, and practical training decisions.
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