(KAIR)--The factors that led to Sunday morning's plane crash that left two dead in Atchison County remain unknown; and, federal investigators say it could take up to a year to complete the final, formal report regarding the fatal crash.

The 64-year-old pilot, Vlado Lenoch, of Bluff Ridge, Illinois and his 34-year-old passenger, Bethany Root, of Atchison, were both killed when the plane crashed late Sunday morning, near Cummings.

The night before, Lenoch flew before a crowd of thousands, showcasing his renowned stunt pilot skills as part of Atchison's Amelia Earhart festival.

Root, the general manager of Atchison's Amelia Earhart Airport, from where the airplane departed, is being remembered as a passionate aviator who, in the words of Atchison City Manager Trey Cocking, “was making a big difference at the airport.”

Federal investigators arrived at the rural crash site early this week, and have been collecting evidence as part of their investigation.

Jennifer Rodi, Senior Air Safety Investigator for the National Transportation Safety Board, ays “the exhaustive and extensive” investigative process could take “from 10 months to a year” to complete.

The plane that carried Lenoch and Root is believed to have been the same 1944 Roth American P-51D Mustang, named Baby Duck, that Lenoch flew as part of Saturday night's Amelia Earhart Festival activities.

According to the report released by the Kansas Highway Patrol, which assisted with the initial investigation into the crash, the plane was traveling southeast, 5 miles south of the airport, when it turned around and then dove towards the ground, where it collided, at 3618 Ness Road.