Shares of

Six Flags

(SIX) - Get Report

went into freefall late Thursday after the company said it was exploring "strategic options" with six of its theme parks, and said it was in danger of not complying with certain bank agreements.

The news sent the shares plunging 19.2%, or $1.43 to $6.01 on Instinet.

The company said the parks may be sold individually or in groups. Another option is dismantling and re-using certain rides and attractions, with the underlying theme park land then sold to real estate developers.

The properties under consideration are Six Flags Darien Lakes near Buffalo, N.Y.; Six Flags Elitch Gardens in Denver; Wild Waves and Enchanted Village outside Seattle; Six Flags Splashtown outside Houston; Six Flags Waterworld in Concord, N.H., and Six Flags Magic Mountain and Hurricane Harbor near Los Angeles.

The company also announced its midquarter numbers, noting that through June 18, revenue was down 1% from the prior-year period. Spending per guest rose 14%, increasing $4.12 per capita, while attendance sunk 13% to about 1.3 million people.

Attendance has been hurt by the season-long closure of the company's New Orleans park due to Hurricane Katrina, reduced school group visits to the Mexico City Six Flags, weather on the West Coast in the first quarter and on the East Coast in May, reduced and delayed marketing costs and the delayed opening of rides, Six Flags said

The company will boost its operating expenses by $15 million (above previous guidance) to $60 million over the year to add employees to improve customer service.

As a result, the company said it is unlikely it would meet its EBITDA guidance for the second quarter.

"The company is at risk of not complying with certain financial covenants in its bank credit agreement," Six Flags said in its announcement. "The company is in discussions with the agent bank and intends to seek amendments to those covenants."

"We're making progress with our strategy to focus on the growth of our strongest assets, reduce the company's debt, and generate increased value for our shareholders," Mark Shapiro, who was named president and CEO of Six Flags in December 2005, said in a statement.

Since March, the company has been focused on ditching its noncore assets to reduce leverage, and focus its resources on its most successful parks.

Six Flags sold the underlying land at Six Flags Astroworld for $77 million; sold assets of its Columbus, Ohio water park for $2 million; announced plans to sell the rides and attractions at its Sacramento water park and is selling two Oklahoma City Six Flags parks. It is also marketing parts of unneeded land at parks in Gurnee, Ill. and Eureka, Mo.