In a preliminary report released Thursday, the National Transportation Safety Board said the fatal April 8 plane crash near Bethel was preceded by several altitude changes before a "rapid, steep descent" to the ground.
Investigators say data transmitted by the Cessna 208 Caravan, operated by Hageland Aviation, shows the plane was flying at 3,400 feet when its altitude changed.
"There were a couple of altitude deviations, followed by a rapid, steep descent," said NTSB spokesman Clint Johnson.
The two pilots on board were killed in the crash -- Derrick Cedars, 42, and Greggory McGee, 46. Officials said that Cedars and McGee were Hageland Aviation employees on a training flight.
According to the report, the crash occurred about 30 minutes after takeoff. The plane left the Bethel Airport at 3:22 p.m. and crashed about 22 miles southeast of Kwethluk at 3:56 p.m., the report said.
Weather data shows the skies were clear and calm at the time of the crash, the report said.
Johnson said investigators are continuing to analyze raw data transmitted by the plane and are looking at factors such as the degree of the altitude fluctuations that took place before the plane's descent.
He said the plane wreckage is expected to arrive in Anchorage by the start of next week, and the investigation team will be conducting a detailed examination.
Reach Devin Kelly at firstname.lastname@example.org or 257-4314.
By DEVIN KELLY