Presidential Executive Orders creating, and final reports of, commissions on…

…the assassination of President Kennedy (EO #11130, 11/29/1963). Final Report.

…the Accident at Three Mile Island (EO #12130, 4/11/1979). Final Report.

…the explosion of the Challenger (EO #12546, 2/3/1986). Final Report.

…the oil spill in the Gulf (EO #13543, 5/22/2010). Final Report.

Note that the 9/11 commission was created statutorily by Congress. Final Report here.