• What is air space and how it is divided

Aviation of Air law is the legal field that deals with all aspects of aviation, from the designing of aeroplanes to flight operations.

In order to navigate properly according to regulations, it is essential to know what is air space, how it is divided and what the norms to transit in it are.

In this post you will learn about the main types of air space and how they are distinguished from each other. We will also revise some common misconceptions about air space. Interested? Let’s go, then!

Definitions of air space

Air space can be defined as the section of Earth’s atmosphere which covers both land and sea and is regulated and administered by a specific state.

Air space is divided in multiple sections in order to guarantee the highest possible safety standards as well as an efficient flow of aeroplanes. We look at each one in turn below.

How air space is divided

Let’s begin with the largest ones first, so it’s easier to understand; we will then move onto the smaller ones.

FIR Flight Information Region

ICAO, the International Organisation for Civil Aviation, has divided the world up into nine regions of flight information, also known as FIR (Flight Information Region). These are:

  • EUR Europe
  • AFI Africa
  • MID Middle East
  • PAC Pacific
  • NAM North America
  • CAR Central America
  • SAM South America
  • NAT North Atlantic
  • ASIA (Asia)

FIRs are, in turn, also divided into smaller FIRs.

For example, in Spain, we have three FIRs: Madrid, Barcelona and The Canaries. Seville has a further FIR that does not act as a separate agent but as a part of Madrid’s FIR. This also occurs in Galicia.

UIR Upper Information Region

Within a FIR two vertical divisions are established: the lower division, still called FIR and the upper one, known as UIR (Upper Information Region).

Even though altitude can vary according to each country’s legislation, in Spain, FIR´s extend from the ground to flight level, that is to 24,500 feet.

UIR, conversely, have their base at FL246 and extend vertically to FL460, at 46,000 feet.

CTA Controlled Terminal Area

If we continue dividing FIR into smaller regions, the next division we find is the control area CTA or Controlled Terminal Area.

CTA must start at a specific altitude, that is, they never start at ground level and extend upwards towards the specified limit.

For example, in Spain, CTA starts at an elevation of 300 metres. This is due to the space between ground and 1000 feet (300 metres) is the layer of free circulation which all types of flying objects occupy.

In Spain, we have eight CTAs.

TMA Terminal Manoeuvring Area

Another term which is closely related to CTA is TMA or Terminal Manoeuvring Area.

TMA are controlled areas established over one or various airports in which a large number of airways or departures and arrivals come together.

The main idea of TMAs is to be able to coordinate instrumental traffic in arrival or departures at the different airports.

For example, in Seville, we have a great TMA which is used to coordinate traffic from Seville, Jerez, Malaga, Granada and Cordoba.

In Spain, we have a total of 12 TMAs.

CTR Controlled Traffic Region

The following divisions we find are CTR or controlled Traffic Region.

CTR are air space controlled areas close to airports and are designed to protect aeroplanes departing and arriving in the lowest flying phases.

Although dimensions may vary, generally, CTR extends to a radio of 5 nautical miles from the reference point of the airdrome. Vertically, they cover from the ground up to, at least, the start of the CTA or TMA.

ATZ Aerodrome Traffic Zone

Finally, we have ATZ or Aerodrome Traffic Zone.

ATZ are controlled airspace that allow increasing the safety of visual traffic in the area surrounding the aerodrome, in case traffic increases significantly. When there is instrumental traffic and an established CTR, ATZ will be within it.

In Spain, ATZ can have a maximum dimension of a cylinder radio 8 km and an altitude of 900 metres.

Types of air space

We have already seen the different divisions that exist in physical airspace but there are also divisions based on their internal characteristics.

To start, and this is the most basic difference, we can distinguish between controlled and non controlled airspace. But we can go even further.

ICAO divides the sky into seven types of air space, named with letters from A to G.

Airspace A, B, C, D and E are controlled, that is, aircraft are subject to controls on the part of the different dependencies of ATS or Air Traffic Services.

Class A

This is the most restrictive type. In it, only instrumental flights, or IFR, are allowed, VFR or visual flights are forbidden.

In this space, all aeroplanes have control and are separated from each other, even though there are no speed restrictions.

In Spain, we have two class A airspace: one in Madrid and one in Barcelona.

Class B

In this type of air space, IFR and VFR flights are permitted. As in class A, all aeroplanes are controlled and separated from each other. There are no speed restrictions here either.

Class C

In this type of air space, IFR and VFR flights are allowed and all aeroplanes are subject to control.

Also, IFR are separated from IFR and VFR, VFR are separated from IFR but only receive information about other VFR traffic.

Instrumental flights do not have speed restrictions while visual flights cannot go over 250 knots up to 10,000 feet.

Class D

In class D, IFR and VFR are permitted and all traffic is subject to control.

Instrumental traffic is separated from other instrumental traffic and receives information about visuals. Whilst visual traffic receives information about instrumental and visual traffic.

From Class D onwards, all flights have a top speed restriction of 250 knots indicated up to 10,000 feet.

If you would like to know more about this, we suggest you read our post about how to measure the different speeds in aviation, which will help you broaden your knowledge on this topic.

Class E

IFR and VFR are allowed but only IFR are subject to control and are separated from other instrumental flights.

All flights receive information about other aircraft, however, this will vary depending on the amount of work each corresponding ATS handles.

Class F

This space belongs to non-controlled traffic. In it, all types of flights are allowed but none are controlled.

Instrumental traffic receives information about other instrumental traffic, but this information can vary depending on the amount of work a controller handles.

Class G

This is the freest space that exists, there is no control or separation for any type of flight.

This is what is known as the free layer of circulation, in which aeroplanes, drones, aeromodels and ultralights fly.

In Spain, the layer of free circulation extends to up to 1000 feet or 300 meters above the ground.

Now you know what air space is, and how important it is

As you have probably seen already, airspace is a very important concept for pilots to understand. Each type of air space carries its own responsibilities.

Although it may be difficult to understand, once you are familiarised with terminology, it is quite simple to remember. It just becomes one of those things you don’t forget!

If you liked this post, we suggest you take a look at our aviation blog, in which you’ll learn how clouds are formed and what a black box is. You simply cannot miss them!

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