Even if the sky may appear always the same, air traffic management requires the airspace to be divided in several classes, named by the first 7 alphabetic letters (A to G).
From A to G, airspaces become less restrictive.
In each airspace type, Air Traffic Services (ATS) provided and flight requirements change. As a rule of thumb, the best way for learning and not forget them is by noticing what is new in each airspace, regarding the previous. Below, all airspaces will be analysed.
Each State may also establish a limited region within the airspace, extending both vertically and horizontally where flying might be prohibited, restricted or to be conducted with caution.
There is a summary of this documentation found here.
Class A airspace is a controlled airspace.
In class A airspace, only IFR flights are permitted (No VFR flights).
All flights are provided with air traffic control service and are separated from each other.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Yes, between IFR | Air Traffic Control, Flight Information, Alerting | No | Continuous, two ways | Required |
In some countries, VFR can be permitted in class A airspace under specific conditions and requirements. All exceptions are published on charts.
Class B airspace is a controlled airspace. In class B airspace, IFR and VFR flights are permitted.
All flights are provided with air traffic control service and are separated from each other.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Yes, between IFR and between IFR and VFR | Air Traffic Control, Flight Information, Alerting | No | Continuous, two ways | Required |
| VFR | Yes, between VFR and between VFR and IFR | Air Traffic Control, Flight Information, Alerting | No | Continuous, two ways | Required |
Class C airspace is a controlled airspace. In class C airspace, IFR and VFR flights are permitted.
All flights are provided with air traffic control service and IFR flights are separated from other IFR flights and from VFR flights. VFR flights are separated from IFR flights and receive only traffic information with respect to other VFR flights.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Yes, between IFR and between IFR and VFR | Air Traffic Control, Flight Information, Alerting | No | Continuous, two ways | Required |
| VFR | Yes, between VFR and IFR. Only Traffic Information between VFR | Air Traffic Control, Flight Information, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Required |
Class D airspace is a controlled airspace. In class D airspace, IFR and VFR flights are permitted.
All flights are provided with air traffic control service, IFR flights are separated from other IFR flights and receive traffic information with respect to VFR flights, VFR flights receive traffic information with respect to all other flights.
IFR aircraft are separated from VFR ones, but VFR aircraft are not separated from IFR ones. VFR needs not to be separated from IFR but they receive traffic information. The responsibility for separation is given to the VFR pilot.
This is known as essential traffic, which by definition means: controlled traffic to which ATC separation is applicable (in this case, IFR traffic) that is not or will not be separated from other particular controlled traffic (in this case, VFR traffic) by the appropriate separation minima.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Yes, between IFR only. Traffic Information between IFR and VFR | Air Traffic Control, Flight Information, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Required |
| VFR | Only Traffic Information between VFR and between VFR and IFR | Air Traffic Control, Flight Information, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Required |
Note that Special VFR traffic shall be separated from other traffic like IFR ones. Special VFR flight is known as a VFR flight cleared by air traffic control to operate within a control zone in meteorological conditions below VMC.
Note that Special VFR rules exist only in some countries. Consult your country regulation publication if you are permitted to use this special rule.
Class E airspace is a controlled airspace. In class E airspace, IFR and VFR flights are permitted.
IFR flights are provided with air traffic control service and are separated from other IFR flights. All flights receive traffic information as far as is practical. Class E shall not be used for control zones.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Yes, between IFR only. Traffic Information between IFR and VFR | Air Traffic Control, Flight Information, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Required |
| VFR | Only Traffic Information between VFR and between VFR and IFR | Flight Information, Alerting | 250KT below 10000ft/FL100 | Not required | Not required |
Class F airspace is a non-controlled airspace. In class F airspace, IFR and VFR flights are permitted.
IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive flight information service if requested.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | Traffic Information between VFR and IFR | Flight Information, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Not Required |
| VFR | No separation | Flight Information on request, Alerting | 250KT below 10000ft/FL100 | Not required | Not required |
A non-controlled airspace is not equal to airspace without air traffic controllers.
Class G airspace is a non-controlled airspace. In class G airspace, IFR and VFR flights are permitted.
IFR and VFR flights are permitted and receive flight information service if requested.
| Type of flight | Separation provided | Services provided | Speed limit | Radio Communication | ATC clearance |
|---|---|---|---|---|---|
| IFR | No separation | Flight Information on request, Alerting | 250KT below 10000ft/FL100 | Continuous, two ways | Not Required |
| VFR | No separation | Flight Information on request, Alerting | 250KT below 10000ft/FL100 | Not required | Not required |
A non-controlled airspace is not equal to airspace without air traffic controllers.