USAir Asks to Skip Pension Payment  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;,  trying to raise money and avoid liquidation, on Monday asked a  judge for permission to skip a big pension payment due this  week, in its first move since filing for protection against  creditors over the weekend.