Prior to the filing, the chairman of Icahn Enterprises had a 9.4 percent stake in the company.
"We believe that over the last few years Doug Lawler and his team have done an admirable job, especially in light of the circumstances. We reduced our position to recognize a capital loss for tax planning purposes," Icahn said in a statement on his site.
The stock extended losses in late trading, falling nearly 2 percent after already tumbling 7 percent in the Monday session.
The sales were made between Sept. 13 and Sept. 19.