A group of retired US Airways pilots, the Soaring Eagles, filed suit today in U.S. District Court in Washington against the PBGC, claiming it underpays pension benefits. Sherwin S. Kaplan, counsel at Thelen Reid & Priest, who represents the group, said the federal pension insurer is "paying many of the retirees, if not all, below the required minimum." The group is seeking a preliminary injunction to force the PBGC to pay the full amount promised the retirees immediately. The airline terminated its pension plan for pilots before emerging from Chapter 11 bankruptcy protection at the end of March. The retired pilots are asking for the full benefits guaranteed by the PBGC, or whatever they were receiving from the airline, and that the PBGC explain how it calculated their benefits. A PBGC spokesman declined to comment.