Thursday's ETF with Unusual Volume: FNX (7/23, 11:28 AM ET) -- The First Trust Mid Cap Core AlphaDEX Fund ETF (FNX) is seeing unusually high volume in afternoon trading Thursday, with over 86,000 shares traded versus three month average volume of about 38,000. Shares of FNX were up about 0.7% on the day.

Components of that ETF with the highest volume on Thursday were Spirit Airlines (SAVE), trading down about 1.7% with over 8.9 million shares changing hands so far this session, and Marathon Oil (MRO), off about 0.7% on volume of over 7.7 million shares. Watsco (WSO) is the component faring the best Thursday, up by about 14.5% on the day, while Caesars Entertainment (CZR) is lagging other components of the First Trust Mid Cap Core AlphaDEX Fund ETF, trading lower by about 4.9%.

For MarketNewsVideo.com, I'm Sayoko Murase.