SEATTLE -- Alaska's Mount Redoubt's first cluster of eruptions in nearly 20 years sent a volcanic ash plume more than nine miles into the air and caused Seattle-based Alaska Airlines to cancel more than 45 flights to areas north of Anchorage since the eruptions began.

A total of six eruptions were detected between Sunday night and Monday night, causing some of the largest mudflows seen in the area for the last 20 years, said Peter Cervelli of the Alaska Volcano Observatory.

The observatory said the latest eruption came at 7:41 p.m. Monday. The five earlier eruptions came late Sunday night and into Monday morning.

On Tuesday, most Alaska Airlines flights to Alaska from Sea-Tac Airport were resuming, though several arrivals were canceled due to the volcano.

Traveler Jake Mountjoy's flight to Alaska was on schedule, but the man admitted to being a little nervous in light of the recent eruptions.

"I don't really know too much about when a volcano erupts, but they told me it all depends on the breeze and visibility and it can also affect the engine. I'm usually pretty comfortable flying, but I guess this is the first time I felt a little uncomfortable," said Mountjoy.

Alaska Airlines said it expects to resume flights throughout Alaska on Tuesday but if the mountain blows again that could change. Travelers should call ahead or look online to check the status of their flights.

Small planes also could be affected. Barry Stanley, owner of Denali Flying Service in Willow, canceled three flights to fly supplies to the Finger Lake area west of Willow on Monday because of the ash.

"You can't fly in this stuff," he said. "Ash is too risky to risk damaging your equipment. I'm not making money if I ruin my stuff."

Ash missed Alaska's largest city, but dusted small communities north of Anchorage. The National Weather Service had an ash advisory in effect until 5 a.m. Tuesday for the Susitna Valley.

The wind took ash away from Anchorage, toward Willow and Talkeetna, near Mount McKinley, North America's largest mountain.

Alaskans had been warned of a pending eruption of the volcano about 100 miles southwest of Anchorage since it became restless in late January. People stocked up on masks, air filters and disaster supplies.

Eight Australians on a backcountry tour holed up in Shell Lake Lodge near Skwentna, about 100 miles northwest of Anchorage, waiting for the ash to settle.

"It's a good half-inch, it's a pretty heavy dusting," Craig Saunders, a Palmer man leading the group on an eight-day snowmobile tour of the Alaska wilds, said Monday.

Ash from Alaska's volcanoes is like a rock fragment with jagged edges and has been used as an industrial abrasive. It can injure skin, eyes and breathing passages.

The young, the elderly and people with respiratory problems are especially susceptible to ash-related health problems. Ash can also cause damage engines in planes, cars and other vehicles.

"Anyone with a pre-existing respiratory problem is advised to stay indoors until the ash settles. If you do need to go out, a mask is recommended," said Dr. Jay Butler, chief medical officer for the state of Alaska.

No injuries were reported.

Based on Mount Redoubt's historical patterns, the activity could continue for weeks or months, Interior Secretary Ken Salazar said during a teleconference.