Another year, another eruption for one of Alaska’s most active volcanoes—and more potential delays on a heavily trafficked international flight path as a result.

The volcano, Bogoslof, erupted most recently this weekend, sending a 36,000-foot ash cloud over the Aleutian Islands. In response to the eruption, experts from the Alaska Volcano Observatory (AVO) issued an aviation warning, since volcanic ash can damage aircraft engines.

According to a report on CNN, this warning could trigger significant delays to international travel. The Bogoslof volcano sits beneath one of the busiest flight paths between Asia and North America, and aircraft often are instructed to fly around or over ash clouds. (In extenuating circumstances, planes have even been grounded due to hazards from the airborne ash.)

This weekend’s eruption marks the second time in the past three months that Bogoslof has gone off; the last time, in May, also triggered some flight delays. All told, the volcano 850 miles southwest of Anchorage has been active since December 2016. 

The most recent eruption prompted an alert level of red, the highest possible alert. The previous eruption, in May, was labeled as a red alert for the first few days, before being downgraded to alert level orange.

As of press time, the Bogoslof eruption hadn’t caused more than minor air traffic delays. Still, because the geologic feature is so unpredictable, it’s completely plausible that subsequent eruptions could create ash clouds even larger than the one from this weekend, prompting a slowdown or shutdown of air traffic in the area.

The most famous volcano-induced travel delays of the past decade occurred in April 2010, when a major eruption of the Eyjafjallajokull volcano in Iceland caused a six-day disruption, Europe’s largest air-traffic shutdown since World War II.

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