What Are Airspace Classes? What Are FIRs?
What Are Airspace Classes? What Are FIRs?

Have you ever wondered how does the airspace above us is managed? If you thought there was only one kind of airspace, think again! It’s time to explore the different classes of airspace.

Before we go into what are the the different Airspace Classes, we need to understand the overall organisation of the airspace between countries.


What are FIRs?

Flight Information Regions, commonly referred to as FIRs, are geographical areas established by aviation authorities used to provide air traffic control services.

FIRs are the foundation of air navigation and a key component of aviation safety.

FIRs are an essential part of aviation safety, as they provide clear and organized boundaries for air traffic controllers to direct aircraft in and out of. This helps ensure that aircraft remain separated, avoiding potential collisions and other dangerous situations.

As air travel continues to grow, FIRs will become increasingly important to ensure a safe and orderly flow of air traffic.

FIRs are (usually) divided in two classes: the bottom part of the airspace as FIR and the upper part as UIR (Upper Information Region).

FIRs (and UIRs) are generally located within a country’s borders and are typically divided up into smaller air traffic control areas that are responsible for providing services to aircraft in their respective areas.

The main classification of these areas is if the air traffic is controlled or uncontrolled. Planes operating in controlled airspace must comply with directions from Air Traffic Controllers, while those in uncontrolled airspace can choose to use any of the air traffic services, such as flight info, alerting, and emergency assistance, if necessary.

In the UK, there are 3 main FIRs: London, Scottish and Shanwick Oceanic.

England and Wales are under the London FIR, Scotland and Northern Ireland by the Scottish FIR, and the Shanwick Oceanic FIR is a region of 700,000 square miles of airspace over the North East Atlantic.

What Are Airspace Classes? What Are FIRs?


What are Airspace Classes?

Airspace classes refer to the different categories of airspace that are used to define the rules of operation in a given airspace. The purpose of airspace classification is to ensure that all aircraft flying in a certain area are operating safely and in accordance with all applicable regulations.

There are generally seven classes of airspace: Class A, B, C, D, E, F and G.

  • Class A airspace is the most restrictive, and it is generally located in areas where the highest levels of air traffic control are required. This airspace typically includes areas around major airports and military operations. Only IFR flights are allowed and the aircraft must have certain equipment onboard. The users are mainly business jets and airlines.
  • Class B airspace is also highly regulated, but it is generally located in areas where the air traffic is much lighter. Aircraft flying in Class B airspace must maintain two-way radio contact with air traffic control. In these areas both IFR and VFR flights are allowed and air traffic provide separation between both type of flights.
  • Class C airspace is the most common type of airspace and it is usually located around medium-sized airports. Aircraft flying in Class C airspace must remain in contact with air traffic control, maintain certain altitude restrictions, and must also follow certain speed restrictions. Here also IFR and VFR flights are allowed, but you must obtain clearance from ATC before being able to enter.
  • Class D airspace is much less restrictive than the other classes and it is typically found around smaller airports. Aircraft flying in this airspace must maintain two-way radio contact with air traffic control and you must obtain a clearance before being able to enter. This class allows for both VFR and IFR flying.
  • Class E airspace is the least restrictive of all and it is generally found in areas where there is less traffic. Aircraft flying in this airspace must obey the same rules as aircraft flying in the other classes. IFR flights must obtain an ATC clearance to enter and must follow air traffic control at all times. But, VFR flights are allowed to enter without a clearance from ATC.
  • Class F airspace allows IFR and VFR flights. But only IFR flights are provided with traffic information and advisory services if requested.
  • Class G airspace allows IFR and VFR flights. All flights are provided with traffic information and advisory services if requested. It is considered uncontrolled and makes up the rest of the area that has not been designated by the other classes.

Regardless of the airspace class, all aircraft must adhere to the same basic rules of operation in order to ensure the safety of everyone flying in the air.

The definition of these classes is provided by ICAO under Annex 11. And the local aviation authority is the one responsible of organising the airspace in these categories.

In the UK, the CAA (Civil Aviation Authority) is the one responsible for this.

The British airspace is divided into only five classes: A, C, D, E and G. ATC clearance is required to enter the controlled airspace classes (A, C, D, E) and the necessary flight rules and air traffic services must be followed.

These spaces are designed to protect users, often commercial airlines, and as such, aircraft and pilots must meet certain standards.

Seraje El Ouahabi
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