https://www.nbcnews.com/news/us-news...ppears-n982386
By Associated Press
DALLAS  — A Boeing 767 appears to have hit turbulence a minute before it  dropped into a rapid descent and smashed into a Texas bay in February,  killing all three people aboard.
The National Transportation Safety Board 
says  "small vertical accelerations" suggest Atlas Air Flight 3591 entered  turbulence soon after the pilots had descended to avoid a band of  precipitation as they approached a Houston airport.
Seconds  after leveling off around 6,200 feet, the cargo plane's engines surged  to "maximum thrust" and it briefly pointed its nose 4 degrees up,  according to flight data. The jet then rapidly swung to point 49 degrees  downward and began its drop toward the muddy bay.
The NTSB does not give a reason for this sharp change in pitch, but says  the plane's stick shaker, which warns of an imminent engine stall, did  not activate. That means it's unlikely the pilots pointed the nose down  to avoid stalling.
The federal agency previously said cockpit audio 
suggests the pilots lost control while passing over Trinity Bay, about 40 miles east of George Bush Intercontinental Airport.
As the plane dropped, the agency says, it accelerated to 495 mph and gradually pulled up to a 20-degree descent...