US Airways Inc., Arlington, Va., hired Aon Fiduciary Counselors as an independent fiduciary for the companys stock, held in several defined contribution plans. US Airways was fiduciary for the employer stock option in US Airways $575.2 million 401(k) Savings Plan, $461.4 million 401(k) Savings Plan for Pilots, $808 million Employee Savings Plan and the $40.8 million Piedmont Aviation Inc. Supplemental Retirement Plan. Asset sizes are as of Dec. 31. Fidelity Investments remains administrator and record keeper for the plans, according to a memo to participants from John C. Honor Jr., vice president of human resources and development.