What is AGL on Boeing 737? (Above Ground Level)

The Boeing 737-800 aircraft is a popular choice for airlines around the world, known for its reliability, efficiency, and comfort. As pilots and aviation enthusiasts, there are numerous technical terms and measurements associated with aircraft that we come across. One such term is Above Ground Level (AGL), which plays a vital role in aviation. In this article, we will explore what AGL means on a Boeing 737-800 and its significance in flight operations.

Before we delve deeper into the concept of AGL, let’s first understand what it stands for. AGL is the abbreviation for Above Ground Level, which refers to the height of an aircraft above the terrain or ground surface below it. It is an essential measurement for pilots to maintain safe and accurate flight operations.

So, what does Above Ground Level mean specifically on a Boeing 737-800? Let’s find out.

Above Ground Level (AGL) on a Boeing 737-800

On a Boeing 737-800 aircraft, the Above Ground Level (AGL) is measured using a radio altimeter, also known as a radar altimeter. The radio altimeter is a specialized instrument that measures the distance between the aircraft and the terrain directly below it by emitting radio waves and measuring the time it takes for the waves to bounce back.

With the radio altimeter, pilots can accurately determine the altitude above the ground, specifically AGL. This data is crucial for various flight operations, such as takeoff and landing, especially in airports with varying terrain or uneven surfaces.

The radio altimeter continuously provides real-time information to the cockpit instruments, enabling the crew to monitor the AGL during critical phases of flight. The display units in the cockpit show the AGL in feet, allowing the pilots to have a clear understanding of their altitude above the ground or obstacles.

During takeoff, knowing the AGL is vital for the pilots to determine if the aircraft has gained enough altitude above the runway surface to retract the landing gear. It also helps in identifying any potential obstructions, such as trees or buildings, that may pose a threat to the aircraft’s safe ascent.

Importance of Above Ground Level (AGL)

The accurate measurement of Above Ground Level (AGL) is crucial for several reasons in aviation. Let’s explore the significance of AGL in more detail:

1. Safe Takeoff and Landing

AGL plays a critical role in ensuring safe takeoff and landing operations. During takeoff, the pilots need to have a clear understanding of the aircraft’s altitude above the ground to make informed decisions regarding gear retraction, obstacle clearance, and acceleration. Similarly, during landing, knowing the AGL helps the crew determine the appropriate time to initiate the flare and touchdown.

The precise measurement of AGL allows pilots to adjust their flying techniques and procedures accordingly, minimizing the risk of accidents or incidents during these critical phases of flight.

2. Terrain Awareness

AGL provides pilots with terrain awareness, which is vital for safe navigation while flying at low altitudes. It helps the crew identify obstacles, such as hills, mountains, or radio towers, that may pose a collision risk. By maintaining a constant awareness of the AGL, pilots can ensure a safe distance between the aircraft and the ground, avoiding any potential hazards.

In some cases, the terrain around an airport may have variations in height or uneven surfaces. Knowing the AGL helps pilots anticipate these changes and adapt their flight profiles accordingly, ensuring a smooth and safe flight for the passengers and crew.

3. Obstacle Avoidance

One of the critical aspects of flight safety is obstacle avoidance. AGL allows pilots to accurately determine their altitude above the ground, enabling them to identify and avoid any potential obstacles in their flight path. This is especially important during low visibility conditions, such as fog or low clouds, where visual references may be limited.

By closely monitoring the AGL, pilots can ensure that the aircraft maintains a safe altitude above the ground or any structures, reducing the risk of a collision and ensuring the safety of everyone on board.


Above Ground Level (AGL) is a vital measurement on the Boeing 737-800 and plays an important role in ensuring safe and efficient flight operations. By accurately measuring the altitude above the ground, pilots can make informed decisions during takeoff, landing, and low-altitude flights. AGL provides pilots with crucial information regarding obstacle clearance, terrain awareness, and obstacle avoidance, contributing to the overall safety and efficiency of the aviation industry.

Next time you’re on board a Boeing 737-800, you’ll have a deeper understanding of what AGL means and its significance in keeping you safe during your journey.

For more information about the Boeing 737-800 aircraft and its technical specifications, visit the official Boeing website.

For More: What is FQPU on Boeing 737? (Fuel Quantity Processor Unit)