US Airways Files for Ch. 11 Bankruptcy  ALEXANDRIA, Va. (Reuters) - US Airways Group Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=UAIR.O target=/stocks/quickinfo/fullquote"&gt;UAIR.O&lt;/A&gt;,  squeezed severely by low-cost rivals and soaring fuel prices  and failing in its drive for new labor concessions, filed for  bankruptcy protection on Sunday for the second time in two  years.