Shares of aluminum producer Alcoa Corp. (AA) tumbled 12.5% in midday trade Monday, putting them on track for the biggest one-day selloff in nine years, after the U.S. extended the deadline (http://www.marketwatch.com/story/treasury-extends-wind-down-period-for-dealing-with-aluminum-giant-rusal-2018-04-23) for dealing with United Co. Rusal . The Russia -based aluminum giant is controlled by Oleg Deripaska , who was sanctioned for his involvement in U.S. elections meddling. Trading volume has ballooned to 8.6 million shares, which is nearly double the full-day average. Alcoa's stock is on track for the biggest percentage decline since it plunged 14.2% on March 30, 2009 . The stock has lost 2.5% year to date, while the S&P 500 has gained less than 0.1%. Among other aluminum companies, Century Aluminum Co.'s stock (CENX) slumped 3.1% in midday trade and Kaiser Aluminum Corp. (KALU) shares shed 1.8%.