As the investigation into last month's plane crash in Montrose continues, the NTSB has ruled out at least one possible cause: icing.
Investigators say pilots of the private jet checked the wings for icing.
The plane was carrying NBC Sports President Dick Ebersol and his 2 sons.
A cockpit voice recorder captured a conversation between the captain and the co-pilot in which they believed the wings were clear of ice.
Icing reduces lift for a plane.
The crash killed the pilot, flight attendant, and Ebersol's 14 year-old son.