SEMICIRCULAR RULE

At the ICAO level, aircraft in flight are obliged to maintain an EVEN or ODD flight level, depending on the flight direction. In most EUROCONTROL member states, such as Romania and Moldova, the rule is West-EVEN, East-ODD. Exceptions to this rule are the countries where the differentiation is made in the North-South direction (such as Italy, Spain, etc.) and the coordination between ATS Units, but non-standard.

The following diagram shows the standard levels depending on the direction of flight in LRBB FIR and LUUU FIR for IFR flights, according to ICAO.

The following diagram shows the standard levels depending on the direction of flight in LRBB FIR and LUUU FIR for VFR flights, according to ICAO.