"As the trial court found, none of the 'red flags' that USAPA ultimately identified constituted red flags at all, and the Plan's decline is explained by unfortunate but ordinary factors. Accordingly, the district court refused to take the unprecedented step of appointing an outside trustee to look again for wrongdoing at the expense of the federal pension insurance program. That decision was fully supported by the trial record, and was not clearly erroneous. Two independent grounds also require affirmance of the decision below, though not adopted by the district court: (i) PBGC's investigative and enforcement decisions are presumptively unreviewable, and (ii) the remedy USAPA seeks, appointment of a replacement trustee, is not 'appropriate equitable relief.' " [U.S. Airline Pilots Assoc. v. PBGC, No. 14-5181 (D.C. Cir., Doc. 1529379, filed Dec. 29, 2014]