Shares of the Arlington, Texas, company at last check rose 3.9% to $41.59.
"Our guests and team members are ready for the return of fun and signature Six Flags thrills in 2021,” Bonnie Weber, senior vice president of park operations, said in a statement.
"Now we are hiring and preparing to reopen every Six Flags park in our system as we continue to work with state and government officials to set firm reopening dates for our parks in California, Illinois, Massachusetts, Mexico City, and Canada," Weber added.
Last year, Six Flags -- like its peer theme-park companies and the entire tourism and leisure industry -- closed operations and cut costs due to the coronavirus pandemic.
The company said it developed its reopening plan in consultation with epidemiologists.
Park reopening dates are subject to change based on local, state, and federal guidelines related to COVID-19, the company said.
The company's Texas property opened with a "Fire & Ice Winter Festival," which runs weekends through Feb. 28. The park will be open for spring break with daily operations from March 12 through 21.
Properties across Georgia; Phoenix, Rockford, Ill., Atlanta, New Jersey, Arlington, St. Louis, Los Angeles, Mexico and others will open on different dates between March and May.
As the parks reopen, Six Flags will offer the best daily-ticket and season-pass prices. The season passes pay for themselves in just two visits.