Former coal company chief executive Don Blankenship has pleaded not guilty to conspiracy charges in the deadliest U.S. coal mine accident in four decades.Blankenship entered the plea Thursday at his first court appearance since he wasindicted last week.He is accused of conspiring to violate safety and health standards at the Upper Big Branch mine in West Virginia. In April 2010, an explosion at the mine killed 29 men.The 64-year-old Blankenship faces up to 31 years in prison if convicted.Blankenship’s Massey Energy Company also operated coal mines in Kentucky in Virginia. The company was sold to Alpha Natural Resources in 2011.
