OSHKOSH, Wis. (AP) -- Investigators say the pilot of a plane that crashed into Lake Winnebago last month lost control during an aerobatic maneuver.

The National Transportation Safety Board says a Piper Cub that went down in the lake near Van Dyne July 25 had left Wittman Airport in Oshkosh with another plane for a sight-seeing flight. EAA AirVenture was under way at the time.

The pilot of the other plane told investigators they flew down the shore of the lake when the other pilot decided to perform a maneuver called a "hammerhead ." The plane turned upward, climbed, turned to the left and started to descend. WLUK-TV reports the plane went upside-down and crashed into the lake, killing both people on board.

Thirty-six-year-old Michelle Palermo of Kimberly and 47-year-old Steven Stales of Makanda, Ill., the pilot, died in the crash.