The PBGC's $2.1 billion claim against US Airways' underfunded pilots pension plan was upheld Monday by a federal bankruptcy court judge in Alexandria, Va. US Airways, which emerged from bankruptcy in March, had said its pilots' pension plan was underfunded by $890 million. "This ruling is a victory for the financial integrity of the federal pension insurance system," said Steven A. Kandarian, PBGC executive director. "It upholds the common-sense view that it should not be cheaper to terminate a pension plan with the PBGC than with a private insurance company." A representative of US Airways could not be reached for comment.