Park spokeswoman Kris Fister said late Sunday that all three people aboard were killed. The Park Service is not releasing the names until families can be notified.
The plane was a Fairchild C-123 registered to All West Freight Inc. of Delta Junction, the Park Service said.
The first responders got to the plane within minutes, but the wreckage was aflame, Fister said.
"The plane pretty much disintegrated," she said.
The plane went down near the park's eastern edge at 3:15 p.m., about 200 yards north of the only major road in the park and about a mile from the park headquarters. It crashed into the south side of Mount Healy, Fister said.
"There were people on the road, buses, other vehicles. The plane coming in was witnessed probably by numerous people," she said.
The fire remains active, she said. Crews will be on the scene through the night dousing hot spots.
Despite some witness accounts, the plane is not military, she said.
The National Transportation Safety Board was expected to arrive on scene Monday morning.
Witness George Clare, of Las Vegas, said he saw the plane flying very low and slowly while he was walking toward the visitor's center near the park entrance. He thought the plane was going to land on a local airstrip, so he proceeded to the visitor's center. Within minutes, people came running in and saying a plane had crashed.
He said the crash caused a column of smoke west of the visitor's center.
"It was a military khaki green kind of color," Clare said. "It was propeller-driven. It was a fixed-wing aircraft, and it had kind of a flat underbelly."
Fister said the fire was initially about one-half acre and grew to about an acre before it was contained. The Alaska Fire Service dispatched eight smoke jumpers to the scene, said Doug Stockdale of the Alaska Fire Service. Park fire crews and volunteer firefighters from the area also fought the blaze.
The park road remains open, but the Rock Creek and Roadside trails, which link the park headquarters and the Denali Visitor Center, are in the area of the crash and are closed.
The crash happened just four days after a military cargo plane crashed at Elmendorf Air Force Base in Anchorage, killing four people onboard.
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