Northwest Air Says Cancels New Ticket Fee  SAN FRANCISCO (Reuters) - Northwest Airlines Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=NWAC.O target=/stocks/quickinfo/fullquote"&gt;NWAC.O&lt;/A&gt;  said on Thursday it canceled a new fee it charged travel  agencies for a round-trip domestic ticket booked through global  distribution systems, effective immediately.