The result of the investigations on pilot fatigue has to do with pilots who are fatigued outside of the regulations. For example, there is a maximum number of hours a pilot can fly in a day, in a month, and a year. There is a minimum requirement for pilots to have a certain amount of rest in a day between flights. The investigations that we've conducted indicated that these pilots were exceeding those maximums and that's why they were fatigued.
On April 13th, 2010. See this statement in context.