What is CAT (I–IIIC) in Aviation? (Operational Performance Category)

In aviation, Operational Performance Category, commonly abbreviated as CAT (I–IIIc), refers to a classification system that enables pilots and air traffic controllers to assess the performance requirements for aircraft operations under various weather conditions. The categorization helps ensure the safety and efficiency of flights by determining the necessary equipment, procedures, and training required for different levels of visibility and approach landing minima.

The CAT system is primarily used for Instrument Flight Rules (IFR) operations, where pilots rely on instruments to navigate and fly the aircraft instead of relying on external visual cues. By defining specific performance requirements, the Operational Performance Category helps pilots and controllers make informed decisions, minimizing the risk of accidents or incidents due to adverse weather conditions. Let’s delve deeper into the different categories of the Operational Performance Category.

Categories of Operational Performance Category (CAT)

The Operational Performance Category is divided into several subcategories, ranging from CAT I to CAT IIIc, each representing different levels of performance requirements. Let’s explore the various categories:

1. CAT I: Basic Performance Requirements

CAT I is the minimum operational performance category, suitable for aircraft operations in moderate weather conditions. A CAT I approach allows for a decision height (DH) of at least 200 feet, with a runway visual range (RVR) of 550 meters (1,800 feet). Pilots using CAT I procedures must have navigational aids that provide accurate course and glide path guidance, such as an instrument landing system (ILS).

During a CAT I approach, the pilot must establish visual contact with the runway environment and be able to make a safe landing if the required visual references are visible at or before reaching the DH. If the visual references are not visible, the pilot must execute a missed approach or go-around procedure.

CAT I approaches are the most common and widely used approach category due to their relatively lower equipment and training requirements. They provide increased operational flexibility for aircraft operators, allowing for safe landings in various weather conditions.

2. CAT II: Enhanced Performance Requirements

CAT II represents a higher level of operational performance requirements compared to CAT I. It is designed for low visibility operations, typically in heavy fog or other reduced visibility conditions. CAT II approaches allow for a lower DH of 100 feet and a lower RVR of 300 meters (984 feet).

In addition to the navigational aids required for CAT I approaches, CAT II approaches typically require additional equipment such as an autoland system. An autoland system enables the aircraft to perform an automatic landing when visibility is limited, ensuring a safe touchdown even in challenging weather conditions.

Pilots operating under CAT II procedures must also undergo specialized training to handle the increased performance requirements and follow specific procedures to ensure safe operations. CAT II approaches provide enhanced capabilities for airlines and airports, allowing for operations in lower visibility conditions and minimizing the impact of adverse weather on flight schedules.

3. CAT III: Maximum Performance Requirements

CAT III represents the highest level of operational performance requirements within the Operational Performance Category. It is further divided into three subcategories: CAT IIIa, CAT IIIb, and CAT IIIc, each representing progressively stricter requirements for aircraft operations in near-zero visibility conditions.

CAT IIIa approaches allow for a DH as low as 50 feet and an RVR as low as 200 meters (656 feet). CAT IIIb approaches lower the DH to as low as 15 feet and the RVR to as low as 75 meters (246 feet). Finally, CAT IIIc represents the most stringent requirements, allowing for an DH of zero feet and an RVR as low as 0 meters (0 feet).

To meet the strict requirements of CAT III operations, aircraft must be equipped with advanced autoland systems, including dual autopilots and multiple redundant systems to ensure precise control during the approach and landing phases. Additionally, CAT III operations necessitate highly specialized training for pilots, maintenance staff, and air traffic controllers to maintain the integrity and safety of the operations.

CAT III operations are crucial for airports and airlines operating in regions prone to foggy or snowy conditions. They enable aircraft to safely land and take off when visibility is significantly impaired, ensuring minimal disruption to air travel even during adverse weather conditions.


The Operational Performance Category (CAT I–IIIc) plays a vital role in aviation by establishing performance requirements for aircraft operations in different weather conditions. From CAT I’s basic requirements to CAT IIIc’s most stringent criteria, each category enables safe and efficient operations by defining the necessary equipment, procedures, and training needed for pilots and air traffic controllers.

Understanding the various categories of the Operational Performance Category allows aviation professionals to make informed decisions during flight planning and ensure the highest levels of safety. By adhering to the performance requirements, pilots and controllers can navigate and operate aircraft with confidence, even in challenging weather conditions.

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