Six Flags Entertainment Corporation (FUN) saw its stock plummet by 5.02% during intraday trading on Thursday, following news of a significant change in its major investor group. The decline comes as Jana Partners, which holds approximately 9% economic interest in Six Flags, announced a key departure from its investor group.

According to a press release from Jana Partners, Dave Habiger has "de-grouped" from the Jana-led investor group to pursue a "complementary opportunity" involving Six Flags. This move has sparked concerns among investors about potential shifts in the activist investor's strategy or influence over the company.

The departure of Habiger from the Jana-led group could signal a change in the dynamics of Six Flags' major shareholders. Jana Partners, founded by Barry Rosenstein in 2001, is known for investing in undervalued public companies and engaging with management teams to unlock shareholder value. The market's negative reaction suggests that investors may be worried about the implications of this change on future strategic decisions for Six Flags.