VFR Cruising Levels — Semi-circular Rule — SERA.5005(g)
General (ICAO)
ICAO Annex 2 §4.7 Cruising levels: VFR cruise flights use a semi-circular rule to avoid head-on encounters at the same level.
Purpose of the semi-circular rule
Semi-circular rules exist to avoid collisions by reducing the probability of opposing traffic at the same altitude.
When does the rule apply?
Semi-circular rules for cruising altitudes are binding above 3000 ft from the ground or water for flights not in climb or descent, provided visibility and cloud distance requirements are met:
- Above 3000 ft AGL (or 1000 ft AGL if higher, AGL is decisive).
- In stable cruise (not climb/descent).
- VMC must be met.
Magnetic track is decisive
For VFR flights, the magnetic track determines the sector for the semi-circular altitude:
| Magnetic Track | VFR cruise level |
|---|---|
| 0° – 179° (eastern half) | odd thousand ft + 500 (3500, 5500, 7500, 9500, 11500, ...) |
| 180° – 359° (western half) | even thousand ft + 500 (4500, 6500, 8500, 10500, ...) |
→ Example: MC 090° → choose FL055 (5500 ft) or FL075 (7500 ft). → MC 270° → choose FL045 (4500 ft) or FL065 (6500 ft).
Europe (EASA / EU)
SERA.5005(g) and SERA Appendix 3 Cruising Levels — equivalent to ICAO Annex 2.
Germany (national)
LuftVO and DFS AIP ENR 1.7 — directly per SERA.