Airspace classes A to G: how German airspace is structured

At the fence, the sky looks simply empty and free. In reality it is divided into floors, and each floor has its own rules. The Airbus on final approach, the glider over the hill and the long-haul jet with contrails are all moving in very different airspaces. The airspace classes A to G determine who may fly where and how, and how strongly air traffic control intervenes. In this guide you learn what is behind the seven letters, which classes Germany actually uses and how German airspace is built from the bottom up.

Airspace classes: the short answer

The International Civil Aviation Organization ICAO divides airspace into seven classes from A to G. Classes A to E are controlled airspace, F and G are uncontrolled. From A to G, control by air traffic control decreases: in Class A only instrument flight is allowed and every flight is monitored. In Class G nobody needs clearance, and air traffic control does not separate.

ICAO only defines the classes. Which of them a state uses where is its own decision. Germany uses classes C, D, E and G. A and B do not occur, and Class F was abolished in December 2014. ICAO adopted the seven-class scheme on March 12, 1990. In the EU, the rules are today anchored in the uniform rules of the air SERA (Implementing Regulation (EU) No. 923/2012).

Three questions every class answers

Behind every airspace class are, at its core, three questions. With them in mind, you can place any class immediately.

• Which flight rules are allowed? There is instrument flight (IFR) and visual flight (VFR). Airliners almost always fly under instrument flight rules, many small aircraft by sight. The difference is explained in detail in the article Visual flight and instrument flight.
• Who needs clearance? A clearance is air traffic control’s permission to enter an airspace or to use a certain route and altitude.
• Who is separated from whom? Separation means that air traffic control establishes minimum distances, laterally, vertically or in time. Those who are not separated must look out for other traffic themselves, following the principle of “see and avoid”.

Added to that are details such as radio requirements, speed limits and the weather minimums for visual flights. The real logic lies in the three questions above.

The seven classes at a glance

Class	Status	Allowed flight rules	Clearance needed	Separated
A	controlled	IFR only	for everyone	all flights from each other
B	controlled	IFR and VFR	for everyone	all flights from each other
C	controlled	IFR and VFR	for everyone	IFR from all, VFR from IFR
D	controlled	IFR and VFR	for everyone	IFR from each other only
E	controlled	IFR and VFR	for IFR only	IFR from each other only
F	uncontrolled	IFR and VFR	none	nobody, IFR receives advisory service
G	uncontrolled	IFR and VFR	none	nobody

Class A: instrument flight only

Class A is the strictest class. Visual flight is prohibited here, every flight needs clearance and is separated by air traffic control from all other flights. Class A is typical for the upper airspace, where almost only airliners operate anyway. The US uses it, for example, from 18,000 feet above sea level to flight level 600.

Class B: all flights separated

In Class B, visual flight pilots may also enter, but only with clearance. Air traffic control then separates every flight from every other, whether by instruments or by sight. Class B is best known from the US, where it surrounds the busiest airports.

Class C: everything controlled, but visual flight possible

In Class C, too, everyone needs clearance. Instrument flights are separated from all other flights, so also from visual flight pilots. Visual flight pilots among themselves, by contrast, are not separated; they receive traffic information about other visual flights. In Germany, C is the class for the upper airspace and the areas above large airports. Visual flights are possible there as controlled visual flight (CVFR) with clearance and radio contact.

Class D: clearance for everyone, separation only for IFR

In Class D, too, everyone needs clearance. But only instrument flights are separated from each other. Visual flight pilots receive traffic information and must keep their distance themselves. In Germany you meet D mainly as a control zone (CTR) around airports, from the ground to a set ceiling.

Class E: controlled only for instrument flight

Class E is something in between. Instrument flights need clearance and are separated from each other. Visual flight pilots may enter without clearance. In Germany, E is the large middle between the near-ground airspace and flight level 100. Below flight level 100 a maximum speed of 250 knots applies there.

Class F: advice instead of control

Class F is uncontrolled. Instrument flights that participate receive an advisory service, but no clearances and no binding separation. In Germany, Class F no longer exists since December 11, 2014. The former F airspaces around smaller airfields with instrument procedures were replaced by Class E or by radio-mandatory zones, so-called Radio Mandatory Zones (RMZ). Great Britain, too, reclassified advisory routes in 2014 that had previously counted as Class F.

Class G: the free airspace

Class G is uncontrolled airspace. Nobody needs clearance, nobody is separated. Air traffic control gives at most flight information, as far as practically possible. In Germany, G lies directly above the ground outside the control zones and once more at the very top above flight level 660. Instrument flight in German Class G airspace is only provided for in connection with an RMZ.

How airspace is layered in Germany

German airspace is best imagined as a stack. From bottom to top, it normally looks like this:

1. Class G begins at the ground. Its ceiling is given above ground and is generally 2,500 feet. In the vicinity of control zones it is lowered to 1,700 or 1,000 feet above ground.
2. Class E adjoins above it and usually extends to flight level 100.
3. Class C mostly begins at flight level 100, near the Alps only at flight level 130, and extends to flight level 660.
4. Class G lies once more above flight level 660.

The airports are cut into this stack. Around every airport with instrument traffic lies a Class D control zone that begins at the ground. Above the large commercial airports such as Frankfurt Airport or Munich Airport, Class C reaches far down and starts directly above the control zone. At smaller commercial airports, this role is partly taken by a Class D airspace that does not begin at the ground.

A word on altitudes: a flight level (FL) does not refer to the current local air pressure but to a standard pressure. FL 100 corresponds to roughly 10,000 feet, FL 660 to roughly 66,000 feet. If you want to understand why airliners mostly fly between FL 300 and FL 400, you will find the explanation in Why aircraft fly at around 10,000 meters.

Layer	Floor	Ceiling	What typically flies there
G (bottom)	Ground	2,500, 1,700 or 1,000 ft above ground	Gliding, ultralight aircraft, traffic patterns, sightseeing flights
D (CTR)	Ground	set altitude above sea level	Airliners on final and climb-out, visual flight pilots on fixed routes
E	2,500, 1,700 or 1,000 ft above ground	usually FL 100	Instrument approaches, business aircraft, small aircraft en route
C	FL 100 (near the Alps FL 130), lower above large airports	FL 660	Airliners in climb, descent and cruise
G (top)	FL 660	–	practically no civil traffic

How these boundaries look on the VFR chart and how you recognize a control zone is shown in the guide Airspace C, D, E, G and control zones: how to spot them on charts. The basics of the chart itself are explained in Reading the ICAO chart.

A flight through all the levels

The structure becomes most vivid when you follow a single flight. Take an Airbus A320 departing from Frankfurt and flying to Munich.

An airliner between two large German airports therefore normally doesn’t touch Class E and G at all. Quite different for a Cessna taking off from a small airfield for a sightseeing flight: it often stays entirely in G and E, needs no clearance and, when in doubt, only talks on the radio with the flight information officer at the airfield. Which radio positions have which job is described in Delivery, Ground, Tower, Approach, Center.

Visual flight conditions: when flying by sight is allowed

For visual flights, each class sets minimum values for flight visibility and cloud clearance. In Germany, in simplified form, the following values apply:

Airspace	Flight visibility	Cloud clearance	Special note
C, D, E up to FL 100	5 km	1.5 km horizontal, 1,000 ft vertical	in C and D, clearance also needed
E above FL 100	8 km	1.5 km horizontal, 1,000 ft vertical	–
D (control zone)	5 km flight and ground visibility	1.5 km horizontal, 1,000 ft vertical	cloud base at least 1,500 ft above ground
G below 3,000 ft MSL or 1,000 ft above ground	1.5 km up to 140 knots	clear of clouds, ground contact	above that, the values are as in C

If the weather in a control zone falls below these values, individual flights under Special VFR are possible with air traffic control’s consent. For you at the fence that means: on days with low clouds and poor visibility, small airfields often go quiet while instrument traffic at the large airport carries on unchanged. How airliners find the runway safely even in bad weather is explained in ILS approach explained.

Why Germany gets by without A and B

The fact that Germany doesn’t use classes A and B doesn’t mean there is less control here. In the upper airspace and above the large airports, Germany uses Class C. There, too, every flight needs clearance, and instrument flights are separated from all other flights. The difference from A lies mainly in the fact that visual flight remains possible in principle as controlled visual flight. For airliners in cruise, this makes no difference, since they fly under instrument flight rules anyway.

Within Class C, too, the work is divided. The airspace over Germany is looked after by DFS German Air Navigation Services. The upper airspace over parts of northwestern Germany, by contrast, is controlled by the control center of Eurocontrol in Maastricht. How neighboring countries organize their air traffic control, you can read in Austro Control and Skyguide.

A look abroad: same letters, different use

Because states choose freely, airspace structures differ, sometimes considerably. If you spot on vacation or listen to foreign aviation radio, you therefore run into different letters.

• USA: Class A extends from 18,000 feet above sea level to flight level 600 and is reserved for pure instrument flight. Class B surrounds the busiest airports, mostly up to about 10,000 feet above sea level. Anyone entering there needs clearance, radio and a transponder with altitude reporting. Around mid-sized airports lies Class C, around smaller fields with a tower Class D. There is no Class F in the US.
• Switzerland: Here too, classes A and B do not occur. Class G generally extends from the ground to 2,000 feet above ground, provided no other airspace such as a control zone lies there.
• Austria: Austria essentially uses classes C, D, E and G, though with different boundaries than Germany. The exact altitudes are in the Austrian aeronautical information publication (AIP).

In practice that means: a Class D control zone in the US is not the same as a German CTR, and an American Class B airspace has no direct counterpart in Germany. When you read airspace information from another country, always check which rules apply there for the respective class.

Special areas that are not a class of their own

Besides the classes there are areas that trigger additional obligations but are not airspace classes themselves. The most important in Germany:

• RMZ (Radio Mandatory Zone): Radio required for everyone, but no clearance and no separation. RMZs surround uncontrolled airfields with instrument procedures.
• TMZ (Transponder Mandatory Zone): Here a transponder must be switched on so that the aircraft remains visible on radar. What distinguishes Mode A, C and S is explained in Transponder Modes A, C and S.
• Restricted areas (ED-R): These areas protect, for example, government districts or military training areas. Temporary restrictions are announced via NOTAMs, see Reading and understanding NOTAMs.

What airspace classes give you as a spotter

You don’t have to fly to benefit from airspace knowledge. It helps you quite practically in several situations.

• Sorting traffic: Airliners stay in C and D, glider pilots and ultralights in G and E. If you spot at small airfields, you will find suitable tips in General aviation spotting and Recognizing small aircraft.
• Finding approach axes: The control zone shows where airliners travel low. Together with the runway direction in use, you know at which end of the runway you should stand. That is explained in Understanding runway direction in use at airports.
• Placing holding patterns: When traffic backs up in front of a large airport, aircraft circle in Class C over fixed points. How to recognize that on the flight tracker is shown in Recognizing holding patterns on the flight tracker.
• Drone at the spot: Control zones and the surroundings of airfields are regulated areas for drones. Before you launch your drone, read Drones at airports: the rules and check the zones in the dipul map.

An example from practice: at the Munich visitors’ hill you see airliners on final approach in the control zone. A small propeller aircraft passing at the edge at the same time, by contrast, flies with tower clearance on a set visual flight route. Both are controlled, but under different rules.

Conclusion

The airspace classes A to G follow a simple logic. The earlier in the alphabet, the more air traffic control intervenes. A allows only instrument flight, B and C separate comprehensively, D and E separate only instrument flights from each other, and F and G are uncontrolled. Germany uses only C, D, E and G of these. The airspace is built like a stack: G at the ground, E above it, C from flight level 100, plus the Class D control zones around the airports. Anyone who knows this order understands why airliners and small aircraft take separate paths and what is happening on the radio.