Jana Partners-led group acquires about 9% stake in Six Flags

An investor group led by activist firm Jana Partners and including NFL star Travis Kelce said Tuesday it has acquired roughly a 9 percent economic stake in Six Flags Entertainment and will press the amusement park operator’s leadership to improve the business. The announcement sent Six Flags shares up 17.7 percent during regular trading and an additional 5.1 percent in afterhours trading.

Jana said the group plans to engage with Six Flags’ management and board of directors to discuss ways to enhance shareholder value and improve the guest experience. The group also includes consumer executive Glenn Murphy and technology executive Dave Habiger, and described its holding as one of the largest stakes in the company.

The move comes as Six Flags reports mounting financial pressure. The company posted a loss of $319.4 million for the first half of the year and reported that attendance fell 9 percent in the three months ended June 29, attributing declines in part to poor weather and a challenged consumer environment in several of its markets. Even after Tuesday’s rally, the company’s shares were down about 47 percent year to date.

Kelce, a tight end for the Kansas City Chiefs who has...