AMR Corp., the bankrupt parent of American Airlines, says that its value has "significantly appreciated" and there may be value for shareholders, Bloomberg News reported yesterday. AMR, which is considering a merger with US Airways Group Inc., notified the Office of the U.S. Trustee of the development in a Jan. 3 letter filed today with the Securities and Exchange Commission. "Depending upon the ultimate strategic alternative adopted and pursued, there exists a reasonable possibility that there may be value for AMR equity holders," AMR attorney Harvey Miller wrote.