Four mainstream movies were released this weekend, all of them competing for the top spot at the weekend box office.

Sci-fi action film Elysium is expected to take the No. 1 slot at the box office with a projected $30 million intake, according to Deadline. The film, which stars Matt Damon and Jodie Foster, was No. 1 Friday with $11.1 million. Elysium is writer-director Neill Blomkamp first film since his Academy Award-nominated 2009 sci-fi film District 9.

The new Jennifer Aniston comedy We're the Millers is projected to come in at No. 2 at the box office. The film, which features Aniston as a stripper, took in $8.5 million Friday and is expected to gross about $26 million over the course of its first weekend.

Despite being rated-R, Elysium and We're the Millers are expected to take the top two slots and beat two family-friendly films: Planes and Percy Jackson: Sea of Monsters.

Disney's Planes made $8.1 million Friday and is expected to debut at No. 3 at the weekend box office. The PG-rated film is a spinoff of Disney-Pixar's Cars franchise and is projected to gross $23.1 million over the weekend, a meager total compared to the debuts of Cars ($60 million) and Cars 2 ($66 million).

The final mainstream debut of the weekend, Percy Jackson: Sea of Monsters is expected to come in at No. 4 at the box office. Sea of Monsters is the sequel to 2010's Percy Jackson & the Olympians: The Lightning Thief but is expected to do worse than the first film's $31 million total. The sequel grossed $4.9 million Friday and is expected to debut with just under $16 million over the weekend.

Last week's debuts, 2 Guns and The Smurfs 2 are expected to drop to No. 5 and 6, respectively, with a projected gross between $10 and $11 million each.

Rounding out the projected top 10 this week are The Wolverine ($8 million), The Conjuring ($6.5 million), Despicable Me 2 ($6.2 million) and Grown Ups 2 ($3.8 million).

Tags: Box Office Elysium we're the millers