Casualties unknown

Seaplane Sinks After Floats Strike Submerged Object on Missouri River (N9691P)

Williston, ND, US

On October 11, 1997, a Piper PA-18-150 (registration N9691P) was involved in an aviation accident near Williston, ND. Investigators recorded the probable cause as: Contact with an unknown object in the water during landing, influenced by the pilot's decision to land due to deteriorating weather without obtaining a weather briefing. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-06-10Data APIEditorial standards

A seaplane sank in the Missouri River after its floats struck an unknown submerged object during landing, forcing the pilot to abort his original destination due to worsening weather.

What happened

The pilot initiated a decision to land prior to reaching the intended destination because of deteriorating weather conditions. During the approach and landing phase on the Missouri River, the aircraft's floats made contact with an unknown object submerged in the water. This impact caused the airplane to roll over and subsequently sink into the river.

The investigation

The pilot reported that he did not obtain a weather briefing before the flight. No further mechanical examination details were provided in the source material.

Findings

Contributing factors included the decision to land in deteriorating weather without a prior briefing and the contact with an unknown object in the water.

Probable cause

Contact with an unknown object in the water during landing, influenced by the pilot's decision to land due to deteriorating weather without obtaining a weather briefing.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001208X08975. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.