Airspace Classes (A-G)

Why classify airspace

Airspace is not uniform: at 33000 ft over the Atlantic you have airliners traveling at 480 knots, separated by minutes from each other. At 1500 ft over Locarno you have a Cessna doing training and a paraglider in thermals.

These two environments need different rules. ICAO classification (Annex 11, Appendix 4) defines seven standard classes — called A, B, C, D, E, F, G — with precise rules for each.

The 7 classes table

Class	VFR allowed	Clearance	Separation	Service
A	❌ No	—	All IFR separated	IFR only
B	✅ Yes	Required	VFR-VFR and VFR-IFR	Control + separation
C	✅ Yes	Required	VFR-IFR; VFR-VFR traffic info	Control + partial sep.
D	✅ Yes	Required	VFR-VFR traffic info only	Control (clearance)
E	✅ Yes	No	IFR-IFR only	Traffic info
F	✅ Yes	No	Advisory service (rare)	Advisory
G	✅ Yes	No	No separation provided	FIS on request

The three golden rules for VFR

For the VFR pilot the three practical rules are:

1. In Class A you don't fly VFR

Airways and upper airspaces (above FL195 in many European countries) are class A — IFR only. VFR never enters.

2. In B, C, D you need clearance

To enter B, C, or D airspace you must: - Establish radio contact - Announce intentions - Wait for explicit clearance

Without clearance, you don't enter. This applies to CTR (class D in CH) and TMA (class C in CH).

3. In E, G clearance not required but transponder may be

In class E and G you fly autonomously. However: - In class E above a certain altitude in many European countries the transponder is mandatory - In RMZ zones (Radio Mandatory Zone) within class G the radio tuned to local frequency is required - In TMZ zones (Transponder Mandatory Zone) the transponder is mandatory

See RMZ / TMZ.

What "separation" means

When a class guarantees "separation", it means the controller actively guarantees your aircraft and others remain at minimum distance:

• Vertical: 1000 ft (below FL290), 2000 ft (above)
• Lateral: 5 NM in radar airspace, more if no radar coverage
• Longitudinal: minimum separation times (e.g. 10 minutes between two IFR on same route)

When a class doesn't guarantee separation (e.g. between VFR in class D, or between everyone in class G), aircraft separate visually by the "see-and-avoid" rule. Each is responsible for seeing and avoiding others.

Classes in Switzerland

Skyguide adopts a simplified structure:

Volume	Class
All airspaces above FL195	C
All TMAs	C
All CTRs	D
External controlled airspace	E
Remaining airspace to surface	G

In practice for Swiss VFR this means: G in valleys and low altitude, D in CTRs, C in TMAs, no A, B, F.

Concrete VFR flight examples and classes traversed

Example 1: Lugano → Locarno

• Take-off Lugano LSZA: class D (Lugano CTR)
• Cruise 4000 ft via Magadino: class G (no radar control)
• Landing Locarno LSZL: class D (Locarno CTR)

One clearance to leave Lugano, one to enter Locarno. In between, total autonomy.

Example 2: Lugano → Zurich

• Take-off Lugano: class D
• Cruise in Ticino valleys: class G
• Climb toward Swiss Plateau: transition from G to E
• Zurich approach: TMA Zurich class C entry (clearance required)
• Zurich landing: class D (CTR)

More class changes, more service changes, more radio.

Summary — to remember

1. A: IFR only. B-C-D: VFR admitted with clearance. E-G: VFR free (with RMZ/TMZ exceptions).
2. In class A you never fly VFR.
3. Swiss CTRs = class D. Swiss TMAs = class C.
4. VFR-VFR separation: always visual (see-and-avoid), even in controlled airspace.
5. In class E/G, watch for RMZ/TMZ.
6. VAC and ICAO 1:500.000 charts show classes — use them.

Sources

• ICAO Annex 11 — Air Traffic Services, Appendix 4 (Airspace classification)
• AIP Switzerland — ENR 1.4 (ATS Airspace Classification)
• Skyguide VFR Guide
• Aero Locarno · Subject 090 — VFR Communications