NASA has been working for the past several months to implement the changes requested by the Columbia Accident Investigation Board. The Stafford-Covey Task Group released their second interim report today, which tracks the status of the Return to Flight effort. Three of the fifteen recommendations have been completed, and they expect to wrap up several more by the summer. One of the most difficult tasks so far has been to eliminate falling debris during launch - it was a piece of foam that fell off the fuel tank that critically damaged Columbia - engineers are worried that the only way to test if the problem has been fixed is by actually launching the shuttle.