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There are situations when an airspace is made of several parts. Each part is described as an airspace volume with a defined horizontal border and specific vertical limits.

Such airspace parts are modelled using the Airspace.type 'PART'. For airspaces used for ATS provision, it is possible to be more specific by using dedicated types, such as: TMA Part ('TMA-P'), FIR Part ('FIR-P'), CTR Part ('CTR-P'), etc.

Type 'PART' airspace


An airspace of type 'PART' has only a geometrical meaning.

Thus, airspaces of type 'PART' are solely used as an auxiliary device to construct an appropriate airspace geometry of a "real" existing airspace (e.g. a TMA or D-Area). The figure below illustrates how such constructions are used:


1Define the central circle as Airspace.type 'PART' with a horizontalProjection.
2Define the polygon airspace to be added, as Airspace.type 'PART' with a horizontalProjection.
3Define the polygon airspace to be subtracted as Airspace.type 'PART' with a horizontalProjection.
4Create the derived geometry by 1 + 2 - 3 (using the AirspaceVolumeDependency).
5By defining vertical limits, the 3-dimensional shape of the airspace is finalized.

Type 'XXX-P' Airspace

On the other side, an airspace of type 'TMA/FIR/CTA/etc.-P' (where P stands for PART) is not necessarily used to define the geometry of a compound airspace, but rather to indicate some specific characteristics of a subsection of a larger airspace. For example, a specific ATS Unit provides services in that airspace part, or different vertical limits are applied. The following figure illustrates such an example:

Typically, the name of such airspace parts includes a number (1, 2, 3, etc.), a letter (a, b, c, etc.) or a geographical direction (East, West, North, etc.), for example Ljubliana TMA 1 and Ljubliana TMA 2.

Coding Examples

Coding examples can be found in the AIP Data Set - Specimen (DONLON).

No.DescriptionXPath Expression




ATS airspace, CTA (Airspace aggregation by copying the geometry), Union of two airspace components

//aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON_CTA'] |

/aixm:AirspaceTimeSlice[@gml:id='ASE_DONLON1_CTA_P'] |




ATS airspace, TMA,  (Airspace aggregation by referencing), Union of two parts

//aixm:AirspaceTimeSlice[@gml:id='ASE_MAGNETTO_TMA'] |

//aixm:AirspaceTimeSlice[@gml:id='ASE_MAGNETTO1_TMA_P'] |

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