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There is little doubt that Robert Downey Jr. is a busy man, but he won't be helping director Jon Favreau fend off invaders in Cowboys & Aliens, the LA Times' 24 Frames reports. Downey Jr. had been set to reunite with Iron Man director Favreau on the graphic novel adaption as the main character, Zeke Jackson, but scheduling became an issue.

Everything had come together quite nicely, including the fact that Mark Fergus and Hawk Ostby, who had co-wrote the screenplay for Iron Man, had also written the first adaptation for Cowboys & Aliens. Alas, it was simply not to be.

For the future of Cowboys & Aliens, plot synopsis, and what RDJ might fill his time with, hit the jump.

While Downey will be missed, DreamWorks will move along with shooting set for sometime this year and a goal of summer 2011 for release. Favreau is still on board to direct, but the search for a new hero will have to begin soon.

As promised, here is the logline for Cowboys & Aliens:

In Silver City, Arizona, Apache Indians and Western settlers must lay their differences aside when an alien spaceship crash lands in their city.

Meanwhile, Downey Jr. has had a monumental resurgence of late and has kept busy, headlining two franchises, including the aforementioned Iron Man and the recently released Sherlock Holmes. Additionally, Iron Man 2 is set to release on May 7, 2010, while the upcoming Todd Phillips' comedy Due Date will bow Nov. 5, 2010.

In other words, Downey Jr. will have a busy 2010, with or without the filming of Cowboys & Aliens, and he has yet to fill what precious little time he has...for now. Just a bit of advice though, don't be shocked if you see a Sherlock Holmes sequel fast-tracked.

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