But the intense action at the Pavlof Volcano, located in an uninhabited region nearly 600 miles (966 km) southwest of Anchorage, has so far not disrupted any regional air traffic, thanks to favorable weather that has made it easier for flights to navigate around the affected area.

Still, the eruption was intense enough for Alaska Volcano Observatory scientists to issue their first red alert warning since 2009, when the state's Mount Redoubt had a series of eruptions that spewed ash 50,000 feet (15,240 meters).

"This means it can erupt for weeks or even months," observatory research geologist Michelle Coombs said of the warning. "I don't think we will be at red for that long, but we are expecting it to go for a while based on its past."

Coombs said affected areas are uninhabited except for some hunting destinations.