How high will Superman fly at the box office? According to sources, "Man of Steel" is gearing up for a $100 million debut at the U.S. box office.

Early buzz on the film has been strong and Warner Bros. is emptying the tank on its marketing campaign for Zack Snyder's $175 million blockbuster.

SEE ALSO: Final "Man of Steel" Trailer Arrives Online

As of Thursday, WB executives were projecting a domestic cume north of $300 million -- possibly more -- with positive word of mouth only strengthening its worldwide potential.

Fandango reported Wednesday that "Man of Steel," opening June 14, is outselling the previous 2013 summer movies at the same time in the sales cycle. The site began offering tickets on May 21.

"Iron Man 3" remains the highest-grossing film of the summer with nearly $1.2 billion globally and $387 million domestically, so WB and DC Comics' caped crusader has a long way to go if he wants to compete with Disney and Marvel's Tony Stark.

Still, box office observers are suggesting muscular B.O. legs for the superhero reboot, which WB will release overseas through the end of June.

"It's very good," one rival exec admits.

Audiences will have to wait until Monday, June 10, to find out just how good, when the film's review embargo lifts at 8:00 p.m. PT, the same night as the film's world premiere in New York.

Directed by Zack Snyder and starring Henry Cavill, "Man of Steel" was produced by Christopher Nolan and Charles Roven.