An independent panel has left little question about BP’s poor safety oversight, its deficient leadership and short-term focus at its U.S. refineries — critical indictments for a company still reeling from the 2005 Texas City, Tex., refinery explosion that killed 15 people and injured more than 100 others.

What remained largely unanswered was how exactly the British company would fill a void in the safety culture at all five of its U.S. refineries, or how long it would take to fix.