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Direction of Cruising Levels

To avoid collision danger between enroute traffic flying on the same cruising level, procedures described in the following article have been established. This also greatly reduces the workload for ATC, as not every aircraft needs to be coordinated individually between two sectors. Within the same sector, it is up to the controller to decide if the procedures will be applied or not. 

Semicircular Cruising Flight Level System

Generally, according to the semicircular cruising flight level system, flights with a planned magnetic course of 360° to 179° fly on odd flight levels. Flights with planned courses from 180° to 359° fly on even flight levels. Where no other operational agreements exist, this system shall be applied for handing off traffic between different sectors. 

Halbkreisflugregel.png

Note that above FL410, the conventional vertical separation minimum (CVSM) applies. Therefore, the odd/even levels will continue in 2000 ft steps. Because of that, FL430 is considered an even level, whereas FL450 is an odd level again. 

For VFR traffic flying above 3000 ft AGL, an additional 500 ft shall be added to each flight level (e.g. FL95, FL105, FL115, etc.). 

Airway Restrictions

Besides the Semicircular Cruising Flight Level System, all airways in Germany have a defined cruising level range depending on the direction of flight. These airway definitions in the AIP overwrite the Semicircular Cruising Flight Level System and may only be overwritten by any further operational agreements (see below). 

The definition of each airway can be found in the AIP IFR chapter ENR 3. 

Example:

For each airway, a special column exists defining the use of cruising level per direction of flight. In our case, airway M736 defines the cruising levels the following way:

  • Traffic flying in the direction from SALLO to BIRMO shall use odd flight levels
  • Traffic flying in the direction from BIRMO to SALLO shall use even flight levels. 

AIP ENR 3.png

This example also shows that the airway definitions sometimes deviate from the general Semicircular Cruising Flight Level System. As traffic proceeding on airway M736 from SALLO to BIRMO (actually flying slightly westbound) is required to use odd flight levels, whereas the Semicircular Cruising Flight Level System would require an even flight level. 

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