LITTLEFIELD, Ariz. (AP) — A federal investigator says the pilot of a small plane that crashed in far northwestern Arizona was flying well below what’s allowed by regulation.

Newly licensed pilot, 19-year-old Daulton Whatcott, and 16-year-old Jaxon Whatcott, were headed to a basketball tournament in Nevada when the single-engine Cessna crashed near the Arizona-Utah border on July 20. The brothers from Clinton, Utah, died.

National Transportation Safety Board investigator Larry Lewis said Thursday that motorists on Interstate 15 saw the plane hit a canyon wall, about 100 feet above the elevation of the road. Lewis says the plane should have been flying at a minimum 500 feet.

Preliminary information indicates the plane rounded a corner and turned upside down before striking the canyon wall and sparking a small fire.

A full report isn’t expected for months.

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