Two people en route to AirVenture at Oshkosh, Wisconsin were killed when their Piper Cub crashed in Lake Winnebago.
The accident is now under investigation by the National Transportation Safety Board, the Experimental Aircraft Association confirms.
The people on board the aircraft were identified as a man and woman, but their names were not released pending notification of family.
Local reports say the Piper immediately sank in about 3m (6.5ft) of water.
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Source: Flight International