Delta Pilots Approve Concession Package  CHICAGO (Reuters) - Pilots at Delta Air Lines Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=DAL.N target=/stocks/quickinfo/fullquote"&gt;DAL.N&lt;/A&gt;  on Thursday ratified a concession package that will save the  carrier \$1 billion a year, in a move the company hopes will buy  it time to restructure outside of bankruptcy.