To ensure safety and efficiency, the ICAO has divided the airspace into different areas and classes. The ICAO specifications generally apply to all countries that are part of the ICAO, but there are individual specific characteristics depending on the country. Below we provide an overview of general concepts for the subdivision of airspace, the specific classes and areas and how this is implemented in the world in general and then also specifically in Germany, Austria and Switzerland.
The airspace
There are various ways in which airspace can be categorised. One of these is the "Flight Information Region" (FIR). This comprises a specific area of airspace in which a Flight Information Service (FIS) and an Alerting Service (ALRS) are provided by the aviation authorities of the country responsible. In many countries, there are Upper Information Regions (defined in Germany as the airspace above FL 245) for airspaces above a certain altitude and corresponding Lower Information Regions (defined in Germany as the airspace below FL 245).
FIS and ALRS are basic services which, according to ICAO, are available to every aircraft travelling in the corresponding airspace. Specifically, each FIR is assigned one or more Area Control Centres (ACC). The controllers there provide FIS and ALRS services, i.e. information to enable safe and efficient flight operations and at the same time services to help aircraft in emergency situations.
FIRs are generally based on national borders and their responsibilities, although there may be several FIRs in larger countries. For Germany, there are the following FIRs for lower airspace:
- EDGG - FIR Langen
- EDMM - FIR Munich
- EDWW - FIR Bremen
For the upper airspace:
- EDUU - UIR Rhine
- EDVV - UIR Hanover
There is only one FIR for Switzerland (LSAS), which covers Switzerland in its entirety. The same applies to Austria with the FIR Vienna (LOVV).
During flight training, e.g. for the LAPL or PPL, you get to know these FIRs or the controllers of the respective ACC very quickly. If you leave the departure area of an airport for a cross-country flight, you will usually register with an FIS service or the controller of the relevant ACC. By registering, you are requesting the use of the basic services described above. In particular, airspace monitoring and information on the possible dangerous approach of other aircraft are FIS services that you will quickly learn to appreciate. In total, FIS includes the following services:
- Traffic information on other aircraft (usually by radar) as far as the controller's workload permits
- Assistance with navigation if the pilot requests help accordingly
- Information on airspaces (e.g. information on whether certain restricted airspaces are active or not) and on the weather
- Information on emergencies or e.g. quick fuel drains
- Receipt and forwarding of flight plans, if necessary
It should be noted that FIS is purely an information service that offers the services mentioned as far as possible. However, FIS does not categorise aircraft and the pilot always remains responsible.
Building on these basic services, which are available to every aircraft in an FIR (regardless of whether you are travelling under VFR or IFR), there are "higher-value" services for certain airspace areas and airspace classes that go beyond the basic services. We will go into these areas and classes in more detail below.
ICAO airspace classes
The ICAO has divided the airspace into different classes. These classes define various guidelines that apply within the respective class. These include, for example
- Flight rules: Flights can generally be operated either according to Visual Flight Rules (VFR) or Instrument Flight Rules (IFR). There are some special features here, such as SVFR (Special VFR), which we will go into in more detail elsewhere
- Type of control: Is the airspace controlled or uncontrolled? There is also a distinction as to who is responsible for the separation of aircraft from each other and for collision avoidance with other aircraft: ATC (Air Traffic Control) or the PIC (Pilot in Command)
- Further guidelines such as maximum speeds, minimum visibility and the necessary horizontal or vertical distances to clouds are also defined for the various airspace classes.
Overall, the ICAO defines classes A to E.
Valid for Germany (expand)
The following table provides an overview of the different classes and the respective guidelines within the class. Although the various countries all follow this ICAO classification, there are certainly differences in the implementation and definition. These are listed in the AIP (Aeronautical Information Publication) of the respective country and should be studied by the pilot in preparation. In the following, we provide details on implementation in Germany. (Information and images from DFS: https://dfs.de/homepage/de/medien/publikationen/sicherer-sichtflug.pdf?cid=ic0)
| Class | Type of control | Flight rules | Staggering of traffic | Maximum speed | Weather specifications for VFR |
| A (Alpha) - Controlled airspace (not available in Germany) | Only IFR allowed | IFR to IFR | |||
| B (Bravo) - Controlled airspace (not available in Germany) | VFR and IFR | IFR to IFR, IFR to VFR, VFR to VFR | |||
C (Charlie) - Controlled airspace  | VFR and IFR | IFR to IFR, IFR to VFR, (traffic information for VFR to VFR) | VFR only: 250kt below FL 100 | Flight visibility: 8km above FL 100; 5km below FL 100 Distance to clouds: vertical 1000 ft; horizontal 1500m | |
D (Delta) (not CTR (control zone around an airport)) - - Controlled airspace  | VFR and IFR | IFR to IFR, (traffic information for VFR) | 250kt below FL 100 | Flight visibility: 8km above FL 100; 5km below FL 100 Distance to clouds: vertical 1000 ft; horizontal 1500m | |
D (Delta) (CTR)- Controlled airspace  | VFR and IFR | IFR to IFR, (traffic information for VFR) | 250kt | Flight visibility: 5km Distance to clouds: vertical 1000 ft; horizontal 1500m Ground visibility: 5km Main cloud ceiling: 1500 ft | |
E (Echo) - Controlled airspace  | VFR and IFR | IFR to IFR; traffic information for VFR as far as possible | 250kt below FL 100 | Flight visibility: 8km above FL 100; 5km below FL 100 Distance to clouds: vertical 1000 ft; horizontal 1500m | |
| F (Foxtrot) - Uncontrolled airspace (not available in Germany) | VFR and IFR | No staggering; traffic information as far as possible | 250kt | Flight visibility: 5km Distance to clouds: vertical 1000 ft; horizontal 1500m | |
G (Golf) - Uncontrolled airspace  | VFR and IFR (in Germany only in conjunction with an RMZ) | No staggering; traffic information as far as possible | 250kt | Flight visibility: above 3000 AMSL or 1000 AGL: 5 km in/below 3000 AMSL or 1000 AGL: 1.5 km, if IAS max. 140 kt Ground visibility Distance from clouds: above 3000 AMSL or 1000 AGL: vertical 1000 feet horizontal 1500 m in/below 3000 AMSL or 1000 AGL: free of clouds | |
Overall airspace structure
The following figure provides an overview of the airspace structure in Germany.
In addition to the classes described above, there are other special areas that have defined vertical and horizontal dimensions. These include, for example, special hazard areas as listed below.
- Prohibited Area: Restricted areas can have various causes, such as military exercises or specially secured events. It is not permitted to fly into restricted areas. They are labelled with a "P" and a serial number. Permanent restricted areas are usually published in the Aeronautical Information Publication (AIP) and on the charts. Short-term areas are announced by NOTAM, often for a specific period of time.
- Restricted areas (Restricted Area)Restricted flight areas can be established permanently or only temporarily. They are intended to avert threats to public safety and are set up to protect certain areas or facilities. They can also be set up for specific events (e.g. G8 summit). They are labelled with an "R" and a serial number. According to the Aeronautical Information Publication: "Flights through active flight restriction areas in Germany are only permitted if
- the nature of the restriction permits,
- transits have been generally authorised by the Federal Supervisory Authority for Air Navigation Services (BAF),
- the responsible air traffic control centre has given its approval in the individual case,
- the user of the area has granted authorisation (for military flights)
- for rescue flights, an agreement has been reached between the operations control centre and the relevant authority responsible for the activities causing the danger in the area with flight restrictions."
- Danger areas: Like restricted areas and restricted flight areas, danger areas are used for flight safety. These areas are usually associated with corresponding military hazards (e.g. military exercises). They are labelled with the letter "D" and a serial number and can be permanent or temporary. In contrast to "P" and "R" areas, flying through danger areas is not restricted or subject to authorisation. However, it is recommended to avoid these areas if possible and to coordinate any flight through them with air traffic control
In addition to the dangers and restriction areas listed, two important areas that also play a role at the start of a flying career are discussed below: RMZ and TMZ:
- Transponder Mandatory Zone (TMZ): By default, a VFR flight in Germany has its transponder locked to 7000 or another frequency assigned by FIS. This is common practice, but the use of a transponder is not mandatory in uncontrolled airspace. When flying into a TMZ, however, the transponder must be switched on or switched to the TMZ-specific number. Furthermore, it is mandatory to be ready to listen on a published radio frequency. In general, the procedure is to ask on the FIS frequency before entering a TMZ whether you should stay on the current transponder code or change.
- Radio Mandatory Zone (RMZ)In an RMZ, radio contact with the specified frequency is mandatory. The VFR pilot must submit an active message on the corresponding frequency before entering the airspace.
Valid for Austria (expand)
In Austria, the entire airspace of FIR Vienna (LOVV) divided into controlled and uncontrolled areas in accordance with ICAO regulations. The responsible Area Control Centre (ACC Vienna) is responsible for FIS and ALRS services.
FIRs
- A single FIR: LOVV - Vienna
Airspace classes
Austria also uses the ICAO classes C, D, E and G. Classes A, B and F do not apply.
- Airspace CAbove FL 195 (up to FL 660) and around larger airports such as Vienna-Schwechat. VFR flights are not permitted here.
- Airspace DControl zones (CTR) around smaller aerodromes (e.g. Graz, Innsbruck) with compulsory coordination.
- Airspace EWide parts of the lower controlled airspace. Staggering only for IFR traffic.
- Airspace G: Uncontrolled airspace. Here VFR applies without mandatory communication - unless you are flying into an RMZ or TMZ.
Special areas
- RMZ (Radio Mandatory Zone) and TMZ (Transponder Mandatory Zone) are used as in Germany.
- Hazardous, restricted and restricted areas are published in the Austrian AIP (e.g. LO R for Restricted Areas).
Other special features
- Flights into airspace C above FL 195 are subject to stricter requirements, e.g. transponder mode S, authorisations and ATC clearance.
Further information: https://austrocontrol.at
Valid for Switzerland (expand)
In Switzerland, the entire airspace is managed by a single FIR: LSAS (FIR Switzerland). Skyguide carries out the checks on behalf of the Federal Office of Civil Aviation (FOCA).
FIRs
- An FIR: LSAS - Switzerland
Airspace classes
Switzerland uses the ICAO classes C, D, E and G. Classes A, B and F do not apply here either.
- Airspace CAbove FL 130 (in the Alps from FL 150) to FL 660 and around larger airports such as Zurich, Geneva.
- Airspace DControl zones of smaller airports (CTR), e.g. Bern, Lugano.
- Airspace EBetween 1000 ft AGL and FL 130, staggered for IFR only.
- Airspace GBelow 1000 ft AGL (except RMZ/TMZ). No air traffic control.
Special areas
- LS-RRestricted Areas
- LS-DDanger Areas
- LS-PProhibited Areas
- All relevant data can be found in the VFR Manual Switzerland or published in the AIP.
RMZ and TMZ
- RMZs (e.g. around Bern or St. Gallen-Altenrhein) are mandatory for incoming flights, as are TMZs.
- Transponder obligation (Mode S) applies above FL 100.
Further information: https://www.skyguide.ch and https://www.bazl.admin.ch
There are many other - often country-specific - classifications and special features with regard to airspace. It is advisable to study the relevant Aeronautical Information Publication (AIP).
Summary
The airspace is divided into different areas and classes that serve the safety, orderly flow and coordination of air traffic. There are various flight information and control services available to pilots within the airspace.
The ICAO defines the airspace classes A to G. Behind this are various regulations on flight rules, traffic separation, maximum speed, weather requirements for VFR flights and more.
There are many country-specific features to consider here, which are described in the respective AIP.
Source references:
DFS Safe visual flight