An ash cloud pushed Mount Etna’s aviation alert all the way to red

Italy’s Istituto Nazionale di Geofisica e Vulcanologia raised Mount Etna’s aviation color code from orange to red at 18:11 UTC on September 16, 2026, its highest alert level, after ash emission from the volcano intensified over Sicily. The Toulouse Volcanic Ash Advisory Center, which tracks ash hazards for aircraft across the region, estimated the plume at roughly 15,000 feet — flight level 150 — in its advisory issued the same evening. Red is the top rung of the four-color aviation scale volcanologists use to warn pilots and air traffic controllers, reserved for eruptions producing ash emission with significant ash cloud height.

The alert affected Catania International Airport, Sicily’s main gateway on the eastern side of the island, which sits close enough to Etna’s summit that ash drifting the wrong direction routinely forces sector closures and flight diversions. Catania handled around 12 million passengers in 2024, making any Etna-driven shutdown a disruption felt well beyond the volcano’s immediate slopes.

Sector Closures at Catania Had Already Begun Before the Red Alert

Etna’s ash problems in mid-September did not begin with the September 16 red code. Two days earlier, the airport had extended the closure of flight sectors B3 and C1, suspending operations and diverting arriving flights to Palermo’s Falcone Borsellino airport instead. “Due to the release of volcanic ash into the atmosphere, the closure of sectors B3 and C1 has been extended, resulting in the continued suspension of flight operations,” the airport said in a public statement reported by The Local, adding that passengers should check flight status with their airline before traveling to the terminal.

That earlier closure came on the heels of a longer disruption: a two-week eruption in August 2026 had already forced the airport shut once, and an American tourist was killed by a lightning strike while hiking a restricted area of the volcano the same month. September’s ash emission arrived as a continuation of an unusually active stretch for Etna rather than as an isolated event.

INGV Sets the Color Code on a Four-Step Scale Built for Pilots

The two agencies driving the alert play distinct roles. INGV’s advisory is the body that actually monitors Etna’s seismicity, gas emissions and visual activity and decides when the color code changes, while VAAC Toulouse translates that assessment into the specific ash-cloud altitude and drift forecasts airlines use to route around the hazard. The scale itself runs green, yellow, orange and red: green means no unusual activity, yellow flags unrest above background levels, and orange signals a heightened chance of eruption or ash emission already underway at low intensity. Red is different in kind, not just degree — it tells airlines an ash cloud capable of damaging jet engines is either present or imminent, and that routing decisions need to account for it immediately rather than as a precaution.

The red designation itself carries no fixed duration — it stays in effect for as long as INGV judges ash emission significant enough to threaten aircraft, and can be lowered again as soon as monitoring shows the emission has eased. Because Etna sits so close to a major international airport, the practical effect of a red code lands on travelers within hours: sector closures, diverted arrivals and delayed departures at Catania, echoing the same pattern the airport had already run through on September 14 and 15 before the color code itself changed on the 16th. At 3,324 meters, or nearly 11,000 feet, Etna is the tallest active volcano in Europe, and its summit craters have erupted repeatedly across the past 500,000 years — part of why Sicilian aviation authorities maintain a standing color-code system for the mountain rather than treating each ash episode as a one-off emergency.

The Red Code Held for Roughly Two Days Before Easing

Ash observation data showed the plume continuing into September 17, with satellite tracking placing the cloud at altitudes as high as flight level 180 at points during that window. By September 18 at 05:35 UTC, conditions had changed enough that a subsequent VAAC Toulouse advisory downgraded the alert from red back to orange, reporting that no ash was identifiable from satellite imagery at that time. That roughly two-day arc — from an intensifying plume on September 16 to a clear satellite pass on September 18 — is typical of the shorter ash-emission pulses Etna produces between its more sustained eruptive phases.

A color code returning to orange does not mean Etna’s activity has stopped entirely; it means the specific ash hazard that justified the red designation has diminished enough that forecasters no longer consider it an acute threat to aircraft. Given the volcano’s pattern through August and September — a two-week closure, a red alert on the 14th, another on the 16th — another advisory raising the code again remains a live possibility rather than a remote one.

Etna’s September Pattern Follows a Summer of Repeated Closures

September’s red alert is the third distinct disruption Etna has caused Catania’s air traffic since midsummer, following the two-week eruption closure in August and the September 14 sector shutdown that preceded the color-code change by two days. Airlines serving Catania have effectively had to build contingency routing through Palermo into their Sicily operations for the second half of 2026, rather than treating each Etna episode as an unplanned exception.

Neither INGV nor VAAC Toulouse has forecast when Etna’s current active phase might taper off entirely; both agencies issue advisories keyed to observed conditions rather than long-range predictions, which is why the color code has moved between orange and red multiple times within a single month instead of settling at one level for an extended stretch.

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This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.