(AP) — Federal investigators blame the pilot for the crash of a small plane nearly a year ago in northeast Nebraska.

The National Transportation Safety Board has ruled out mechanical problems for the April 27, 2013, crash about two miles southeast of Norfolk. The pilot, 26-year-old Dale Butler, and passenger, 24-year-old Amy Brobst, of Fort Collins, Colo., were killed.

The board report says the accident was caused by Butler’s decision “to fly at a low altitude and his subsequent failure to see and avoid power lines.” The report says the pilot might not have seen the lower power lines the plane struck because he may have been focused on a set of high tension power lines about a half-mile from the crash site.