National Transportation Safety Board

The National Transportation Safety Board said it itended to investigate the cause of the crash, which remained unknown.

“Caltrans is reviewing the National Transportation Safety Board’s recommendations and will respond to its request once the review is completed.”

In a March 18 report, the National Transportation Safety Board identified a total of 68 bridges across the United States as not having undergone a vulnerability assessment based on recent vessel traffic.

But low- to no-casualty events are the most common of air accidents: Between 2010 and 2020 there were an average of 29 accidents a year, according to National Transportation Safety Board.

Jennifer Homendy, chair of the National Transportation Safety Board, said the investigation into the crash was in its "early stages" and it was too soon to tell what caused it.