The National Transportation Safety Board says prior to the fatal small airplane crash just north of Anchorage on April 20, the aircraft collided with a bald eagle.
The crash killed all four people on board, including 36-year-old Sarah Glaves who had strong ties on the Kenai Peninsula.
The NTSB says this is the first fatal civilian plane crash in the nation following an impact with a bald eagle.
The pilot, co-pilot, and two passengers were killed after the plane crashed approximately 20 miles north of Anchorage.
Investigator Shaun Williams with the NTSB says previous crashes involving eagle strikes resulted in serious injuries but not deaths.
Williams says the NTSB found an unknown substance on the wreckage after the crash.
The Smithsonian Institution in Washington, D.C. determined that to be feathers and other materials that came from an immature bald eagle.
The NTSB says a collision with a bird of that size could have altered the flight path or caused enough damage to create control issues for the pilot.
Investigators are still working to finalize the crash report, expected to take up to a year.