UPDATE: In a bold move, the NTSB recommended seat belts on all school buses after the deadly Woodmore crash.  

"This will be a historic day," said NTSB chairman  Robert L. Sumwalt III in a board meeting Tuesday.

The board said the lack of belts on the bus was a contributing factor in the deadly 2016 crash.

READ MORE | NTSB discusses Woodmore bus crash

The National Transportation Safety Board has also adopted a three-part probable cause in the Woodmore Elementary bus crash that killed six children in 2016.

According to the NTSB, the three-prong cause is:

  1. School bus driver's excessive speed and cell phone use, which led to the loss of vehicle control.
  2. Durham School Services failed to provide adequate bus driver oversight allowing an inexperienced bus driver to operate a commercial vehicle with escalating risky driving behavior that could lead to the unsafe operation of the school bus.
  3. The Hamilton County Department of Education's lack of follow up to ensure that Durham School Services had addressed a known issue.

The probable cause was originally amended from the first item as a single probable cause. This happened when NTSB chairman Robert L. Sumwalt III recommended the three-pronged cause. Then the board voted to approve the measure.

The Woodmore crash findings were released Tuesday along with findings from a Baltimore bus crash that was driven by a man who had a seizure while driving that bus.