EXCLUSIVE: George Clooney Replacing Robert Downey Jr. in 'Gravity'

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George Clooney will star opposite Sandra Bullock in Gravity, Warner Bros.’ and Legendary Pictures' 3D outer space thriller that has become a game of musical chairs for actors.

The initial pairing for the Alfonso Cuaron-directed project -- about a female astronaut struggling to survive and trying to make it to Earth after a disaster in space -- was to have been Angelina Jolie and Robert Downey Jr. Then came a protracted series of reversals that saw Jolie leave and come back, and actresses Marion Cotillard, Scarlett Johansson, Blake Lively and Natalie Portman involved with the movie to varying degrees, all within the last eight months.

Downey stuck with the project throughout the various casting changes but in mid-November, just as things looked set with Bullock, he bailed.

Warner considered scrapping the project but conducted a Hail Mary search for the male lead who, while doesn’t carry the movie, is still pivotal in the first act.

Clooney will play an astronaut who survives the space disaster alongside Bullock. The studio is eyeing a spring start of production after CAA-repped Clooney directs Ides of March, the adaptation of the political drama that has Ryan Gosling and Paul Giamatti attached to star.

David Heyman (Harry Potter) is producing. Lynn Harris is overseeing for the studio.