LOS ANGELES — The Academy Museum of Motion Pictures is starting to feel a little cursed. Since the project was announced in 2012 — with an opening expected in 2017 — setbacks have included sparring architects, the discovery of mastodon fossils by excavation crews, a budget that ballooned by roughly 90 percent, the ouster of its founding director and now, for the second time, the coronavirus pandemic.

On Friday, the museum pushed back its opening to Sept. 30, 2021, from April 30, citing the virus and difficulty forecasting when public life may begin to normalize. The pandemic already scuppered a planned opening this week. “With the current surge of Covid-19, it would be irresponsible to maintain an April opening,” Bill Kramer, the museum’s director and president, said by phone. “It’s not because we aren’t ready. Work has been moving forward. We’re completely on track.”

Ted Sarandos, chairman of the museum’s board of trustees and Netflix’s co-chief executive, added in a statement: “It’s just a matter of patience, for all of us, as we look ahead to opening our doors on Sept. 30.” A private gala was set for Sept. 25.

How did the museum select those dates? This month, for instance, Warner Bros. said it would still be too difficult to release movies normally by next December because of the pandemic.

Mr. Kramer said summer was not an ideal time to inaugurate a cultural institution (too many people scattered here and there). An early September opening would collide with the Telluride and Toronto film festivals.

Had the $482 million museum stuck to its April plan, a marketing campaign would have started next month. Hiring was also set to begin for gallery guards and ticket takers.

For all of its stops and starts, the museum has gotten its act together under Mr. Kramer, who was hired last year. (He previously served as vice president of development for the Brooklyn Academy of Music.) In recent months, the museum has hired the film scholar and Turner Classic Movies host Jacqueline Stewart as its chief artistic and programming officer; repaired relationships with Hollywood collectors; attained LEED eco-friendly certification; and reached its pre-opening fund-raising goal of $388 million. Despite difficult working conditions because of the coronavirus, crews have installed exhibits, including a 25-foot-long, 45-year-old fiberglass model of the mechanical shark that Steven Spielberg used to film “Jaws.”

Mr. Kramer called the shark, nicknamed Bruce, “shockingly cool.”