Aviation Colour Codes

The Aviation Colour Code system is based on four colours and is only intended for use by the international civil aviation community. The system is defined by the International Civil Aviation Organization, and GNS Science allocates the levels for our volcanoes – this information is in our Volcanic Alert Bulletins. The Aviation Colour Codes provide the aviation community with information about volcanic activity and the potential presence of volcanic ash in the atmosphere. This information enables the aviation sector to make decisions about aviation safety and flight routes, especially for long-haul flights.

Example: Aviation Colour Code Orange indicates that a volcanic eruption is underway but with little or no ash being produced.

ICAO Colour Code Status of activity of volcano
GREEN Volcano is in normal, non-eruptive state. or, after a change from a higher level: Volcanic activity considered to have ceased, and volcano reverted to its normal, non-eruptive state.
YELLOW Volcano is experiencing signs of elevated unrest above known background levels. or, after a change from higher alert level : Volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE Volcano is exhibiting heightened unrest with increased likelihood of eruption. or, Volcanic eruption is underway with no or minor ash emission. [specify ash-plume height if possible].
RED Eruption is forecasted to be imminent with significant emission of ash into the atmosphere likely. or, Eruption is underway with significant emission of ash into the atmosphere. [specify ash-plume height if possible].