Airspace C, D, E, G and control zones: how to spot them on charts

You are standing at the fence, and a Cessna passes at low altitude across the approach axis while the Airbus behind it stubbornly stays on the glide path. That is no coincidence. Both are moving in clearly delineated airspaces with their own rules. Anyone who can read airspace on charts understands this order. They see at a glance where a control zone ends, where small aircraft move freely and why traffic bunches up at certain places. This guide explains Classes C, D, E and G, the control zone and the most important special areas. It also shows how to read all of that on the ICAO chart and in digital map services.

Airspace in Germany: the short answer

The airspace over Germany is divided into four classes: C, D, E and G. Each class determines three things. First, whether pilots need air traffic control clearance. Second, which traffic is separated from each other. Third, which minimum visibility and cloud clearance apply to visual flights. Classes A and B do not occur in Germany. The former Class F was abolished in December 2014 with the switch to the European SERA rules.

Put simply, control gets stricter from the bottom up:

• Class G is at the very bottom, directly above the terrain. No clearance is needed here.
• Class E adjoins above it and usually extends to flight level 100. Only instrument flights need clearance here.
• Class C mostly begins at flight level 100 and extends to flight level 660. Above large commercial airports, C starts much lower.
• Class D you find mainly as a control zone (CTR) around airports with instrument traffic, from the ground to a fixed ceiling.

You can find the systematic overview of all classes from A to G, including the internationally used ones, in the article Airspace classes A to G. This one is about the classes that actually occur in Germany and what they look like on the chart.

The four classes in detail

Class G: low and uncontrolled

Class G is the uncontrolled airspace directly above the ground. Its ceiling is always given above ground and depends on how close a control zone or RMZ is: 2,500, 1,700 or 1,000 feet above ground. Nobody needs clearance here, and there is no separation. Instrument flights in G are only provided for in connection with an RMZ.

For visual flights, relaxed conditions apply in G as long as the aircraft is low and slow. Below 3,000 feet above sea level or 1,000 feet above ground, a flight visibility of 1.5 kilometers is enough at speeds up to 140 knots. The aircraft must stay clear of clouds and have ground contact. Above that, 5 kilometers of flight visibility and a cloud clearance of 1.5 kilometers horizontally and 1,000 feet vertically apply.

For you as a spotter, G is the airspace of glider pilots, ultralight aircraft, motor gliders and many sightseeing flights. Anyone spotting at small airfields almost always deals with this airspace. How to find such airfields in the first place is in the guide Finding small airfields on maps, and tips on the scene are provided by General aviation spotting.

Class E: the big controlled middle

Above G lies Class E. It generally begins at 2,500 feet above ground. Around control zones, the floor is lowered to 1,700 or 1,000 feet above ground. That puts instrument approaches in controlled airspace early. Upward, E usually extends to flight level 100.

In E, only instrument flights need clearance. They are separated from each other. Visual flight pilots may enter without clearance and receive traffic information where possible. Below flight level 100, a maximum speed of 250 knots applies. For visual flights up to flight level 100, a flight visibility of 5 kilometers and a cloud clearance of 1.5 kilometers horizontally and 1,000 feet vertically are required, and above that 8 kilometers of flight visibility.

Class C: the upper levels and the big airports

Class C mostly begins at flight level 100, near the Alps only at flight level 130, and extends to flight level 660. Above it lies Class G again. Above the large commercial airports, though, C reaches far down and starts directly above the control zone. These areas show up on the chart as stepped structures. The farther from the airport, the higher the floor.

In C, everyone needs clearance. Air traffic control separates instrument flights from all other flights, including visual flight pilots. Visual flights there are only possible as controlled visual flight (CVFR), that is, with clearance, radio contact and precise guidance from air traffic control.

Class D: control zone and D areas

You encounter Class D in two forms. Most often as a control zone around an airport. In addition, above some control zones of smaller commercial airports there is Class D airspace that does not begin at the ground. It takes on the role that Class C plays at large airports, but without the CVFR requirement.

In D, everyone needs clearance. Instrument flights are separated from each other, and visual flight pilots receive traffic information. For visual flights, 5 kilometers of flight visibility and 1.5 kilometers horizontal and 1,000 feet vertical cloud clearance apply.

Class	Typical location in Germany	Clearance needed	Separated	Typical traffic from a spotter’s view
C	from FL 100 to FL 660, lower above large airports	for everyone	IFR from IFR and VFR	Airliners in cruise and in the approach area of large airports
D (CTR)	from the ground to the ceiling around airports	for everyone	IFR from IFR	Airliners on final and climb-out, visual flight pilots on fixed routes
D (not CTR)	above control zones of smaller airports	for everyone	IFR from IFR	Approach traffic of regional airports
E	from 2,500, 1,700 or 1,000 ft above ground to FL 100	IFR only	IFR from IFR	Instrument approaches, business jets, cruise flights of small aircraft
G	from the ground to the E floor	none	nobody	Gliding, ultralights, traffic patterns, sightseeing flights

The control zone: the heart of the area around the airport

The control zone, internationally CTR for Control Zone, is the most important airspace for spotters. It begins at the ground and extends to a fixed ceiling, which is given in feet above sea level. In Germany, control zones are Class D airspace. The tower directs all takeoffs, landings and transits within it.

For visual flight pilots, stricter conditions apply in the CTR than in the surroundings. The cloud base must be at least 1,500 feet above ground, and ground and flight visibility must each be at least 5 kilometers. Anyone wanting to enter needs clearance and must monitor the tower frequency. If the weather is below these values, individual flights under Special VFR are possible with air traffic control’s consent. Aircraft without radio, such as paragliders and hang gliders, generally stay out.

How to recognize the shape of a CTR

The shape of a control zone is no coincidence. It follows the runways and the approach and departure paths. Many control zones are elongated rectangles that stretch in both directions along the approach axis. But there are also round, composite and irregular shapes. A well-known example is Cologne/Bonn Airport. Because the runways cross there, the control zone also has a cross shape.

For spot planning, this is a practical hint. The long arms of a CTR show you along which lines the airliners travel on final and climb-out. There they are low enough for photos from approach corridors. Which direction is active on a given day is decided by the wind. That is explained by the guide Understanding runway direction in use at airports. How the approach itself works technically you can read in ILS approach explained.

Compulsory reporting points and HX zones

On VFR charts, compulsory reporting points are marked on the edge of many control zones. Visual flight pilots enter and leave the CTR via these prominent terrain points, such as freeway interchanges. Their names mostly follow the compass direction from the airfield, for example WHISKEY for a point in the west. Anyone listening to aviation radio meets these names constantly. With the chart beside you, you can then work out from which direction the next Cessna is coming. Pilots pronounce the letters according to the ICAO spelling alphabet.

Not every control zone is active around the clock. At large airports it is. Many smaller and military control zones, by contrast, are only switched on as needed. On the chart they carry the addition HX, meaning no fixed operating hours. If such a CTR is not active, the surrounding airspace structure applies there.

Special areas: RMZ, TMZ and restricted areas

Besides the classes, every aeronautical chart shows further areas that trigger their own obligations.

• RMZ (Radio Mandatory Zone): In an RMZ, radio contact is mandatory, also for visual flight pilots. Clearance is not needed, and there is no separation. RMZs surround uncontrolled airfields where instrument flights are permitted and typically extend from the ground to about 1,000 feet above ground, where Class E begins. In Germany they replaced the former F airspaces in 2014. A well-known example is the Egelsbach airfield south of Frankfurt.
• TMZ (Transponder Mandatory Zone): Here a switched-on transponder is mandatory. That way, even aircraft without radio contact remain visible on radar. What distinguishes Mode A, C and S is explained in Transponder Modes A, C and S.
• Restricted areas (ED-R): The abbreviation is composed of the ICAO region E, the country code D for Germany and R for restricted. Such areas protect, for example, government districts, power plants or military training areas. ED-R146 lies over Berlin’s city center. Some areas are permanently active, others only at certain times or on announcement via NOTAM.

Temporary restrictions, for example at major events or state visits, are not on the printed chart. They are published via NOTAMs. How to read them is shown in Reading and understanding NOTAMs.

How to read airspace on the ICAO chart

The official VFR chart in Germany is the ICAO chart 1:500,000. One centimeter on the chart corresponds to five kilometers. The publisher is the DFS German Air Navigation Services. The chart is published annually, usually at the end of March. Airspace boundaries, altitudes, airfields, radio beacons and obstacles appear in the blue air traffic control overprint over the topographic map. Control zones that begin at the ground are additionally shaded within their blue boundary. That makes them stand out immediately. The basics on scale, terrain and symbols are explained in Reading the ICAO chart: basics.

Most airspace boundaries carry an altitude label with two values: the ceiling on top, the floor below. Here you have to distinguish three references.

Notation	Meaning	Example	What to watch for
GND	Earth’s surface, that is, the ground	Control zone from GND	Floor at the ground, typical for CTR and RMZ
ft GND / AGL	Feet above ground	E from 1,000 ft GND	Follows the terrain, over hills the boundary is higher
ft MSL	Feet above mean sea level	CTR up to 2,500 ft MSL	Fixed height, independent of the terrain below
FL	Flight level, based on standard air pressure	C from FL 100	Applies at altitude, FL 100 corresponds roughly to 10,000 feet

Lowered E floors are also marked on the chart as areas of their own with an altitude figure. Around many control zones you thus see a kind of onion: inside the CTR at the ground, around it a ring with E from 1,000 feet above ground, farther out E from 1,700 feet. And only in open country does E from 2,500 feet apply. What colors and lines look like in detail is set by the legend of the respective chart edition. Taking a look is worthwhile before every new season.

Digital charts and flight trackers: airspace on screen

The printed ICAO chart is the official reference. For research at the computer, though, there are digital alternatives. Open data projects like openAIP display airspace, airfields and navigation aids on a freely zoomable map. For spotters, that is often the most convenient way to lay the shape of a control zone over a satellite image. How to explore an airport site in advance on screen is shown in Exploring airports with Google Maps and Google Earth. For details on the airport grounds themselves, that is taxiways, aprons and runways, the aerodrome chart from the aeronautical information publication (AIP) is the right source. You can read more in Reading AIP aerodrome charts.

It gets exciting when you combine the airspace chart with live data. On flight tracker services you see the altitude and course of aircraft. With the airspace structure in mind, you recognize when an airliner enters the control zone, where it drops below the E floor and why small aircraft fly around the outside. The data fields on these maps are explained in Flight tracker symbols and colors. The technology behind the positions is described in Flight tracking with ADS-B for spotters.

What airspace structure gives you as a spotter

Airspace knowledge will not become pilot knowledge for you. But it is a very useful tool, in several situations.

• Finding approach corridors: The control zone shows the axes on which airliners travel low. Combined with the runway direction in use, you know at which end of the runway you should stand.
• Gauging small aircraft: Reporting points and traffic patterns in Class G explain where general aviation flies. To go with that, Recognizing small aircraft helps you with identification.
• Understanding helicopters: Rescue and police helicopters often fly low and straight through control zones, with tower clearance. How to follow them live is shown in Finding helicopters on the flight tracker.
• Placing radio calls: When the tower issues a clearance “to the reporting point” or “leaving the control zone”, the chart tells you exactly where the aircraft is. Whether and how you may listen in is clarified in Listening to aviation radio: the legal situation.
• Drone at the spot: Control zones and the surroundings of airfields are regulated areas for drones. Before you launch your drone at the airport, read Drones at airports: the rules and check the zones in the dipul map.

An example: Stuttgart Airport sits on the Filder plain at just under 390 meters, or about 1,300 feet, above sea level. From the ceiling of its control zone, which is given on the chart in feet above sea level, you have to subtract this field elevation. So noticeably less room remains above the terrain than the number suggests at first glance. Such values can change with a new chart edition. So always check the current edition.

Conclusion

The airspace structure in Germany is more manageable than the many lines on the chart suggest. At the very bottom lies free Class G. Above it adjoins E, which is controlled for instrument flights. At the top and around large airports, C applies. Added to that are the Class D control zones, which protect traffic at the airport from the ground up. On the ICAO chart you recognize them by the blue overprint, the altitude labels and the shaded control zones. Anyone who keeps GND, MSL and FL apart reads every boundary correctly. For spotters this is more than theory. The shape of the airspace explains approach axes, VFR routes and radio traffic and makes the search for spots more targeted.