NEW YORK, Oct 21 (Reuters) - Activist investor Jana

Partners owns a 9% stake in Six Flags Entertainment ( FUN ) and has

teamed up with football star Travis Kelce to push the theme park

operator to improve marketing and customer experiences.

Jana Partners' Scott Ostfeld disclosed the position at the

13D Monitor Active Passive-Investment Summit in New York on

Tuesday. On Friday, the company said it added an executive from

activist hedge fund Sachem Head Capital Management to its board

at a time the theme park operator is facing pressure from

several investors to perform better.