Forward Air Corp., Greeneville, Tenn., announced plans to offer 3 million shares of common stock to the public.The company will sell 1 million shares and its chairman, Scott M. Niswonger, will sell the remaining 2 million. The sale will reduce Niswonger’s ownership in the company from 49.4% to 31.1% of the total shares outstanding.Underwriters for the secondary offering include BT Alex. Brown, Morgan Keegan & Co. and Scott & Stringfellow.Forward Air currently has about 6.4 million shares outstanding. Its stock is traded on Nasdaq under the symbol .