* Jana Partners urges Six Flags to explore sale

* Richard Haddrill named executive chairman of Six Flags

* Six Flags stock up 10% this year, down 56% over 12

months

* Investors have limited time to launch proxy fight

By Svea Herbst-Bayliss

NEW YORK, March 25 (Reuters) - Theme park operator Six

Flags Entertainment ( FUN ) on Wednesday announced a change in

leadership on its board, naming Richard Haddrill as executive

chairman.

Last week activist investor Jana Partners told the company

in a letter seen by Reuters that it wants the company to

immediately appoint a new chairman and explore a sale.

Marilyn Spiegel, who was named chair in January, will serve

as lead independent director. She has been a director at Six

Flags since 2023.

Haddrill previously served as executive vice chairman of the

board of Scientific Games and was chief executive of Bally

Technologies.

"This change in board leadership is an important step in the

right direction," a representative for Jana said on Wednesday

morning.

Reuters reported last week that Jana's managing partner Scott

Ostfeld wrote to the company that the hedge fund has concerns

about the board's ability to "deliver" for shareholders and

calls on the company to engage with buyers.

Jana publicly expressed support for Six Flags new CEO John

Reilly, who was appointed in November, but wrote last week that

it wanted to see a new board chair after months of private

engagement raised concerns about the group's effectiveness.

Investors have only a few more days to decide on possibly

launching a proxy fight by nominating director candidates to

replace sitting board members.

The theme park's stock price has climbed 10% this year but

remains down 56% over the last 12 months. In February, Reilly

had said that while 2025 results had come in short of the

company's expectations, "the work completed over the past year

has strengthened the foundation of our enterprise."

He said the company improved park infrastructure, added new

attractions, upgraded technology and enhanced food and beverage

offerings. He also said the company's efforts are sure to

"restore profitable growth that is sustainable over time."

Jana is not the first activist investor to push Six Flags

for changes. In October, only days before Jana's position was

unveiled, the company added an executive from activist hedge

fund Sachem Head Capital Management, which owns roughly 5% of

the company, to the board.