Los Angeles, March 28 : Hollywood star Matt Damon said that filmmaker Christopher Nolan's "Oppenheimer" runs a hefty three hours long. On the red carpet for 'Air', in which he co-stars, Damon also talked about Nolan's upcoming historic drama in which he appears alongside Cillian Murphy, reports 'Variety'. "It's three hours. It's fantastic," Damon said, revealing that he's seen 'Oppenheimer'. "Cillian is phenomenal. He's everything you would want him to be," Damon told Malkin. "I think it's almost three hours. It goes so fast, it's great." Directed by Ben Affleck, 'Air' stars Damon as Sonny Velasco, who led Nike to pursue the endorsement of Michael Jordan and the creation of the Air Jordan basketball sneakers. 'Air' opens April 5 and co-stars Affleck, Viola Davis, Jason Bateman and Chris Messina. 'Oppenheimer' stars longtime Nolan collaborator Murphy as theoretical physicist J. Robert Oppenheimer, the director of the Manhattan Project and the "father of the atomic bomb." The cast also includes Emily Blunt, Robert Downey Jr., Florence Pugh, Rami Malek, Benny Safdie, Josh Hartnett, Dane DeHaan, Jack Quaid, Matthew Modine, Alden Ehrenreich, David Krumholtz, Michael Angarano and Kenneth Branagh. 'Oppenheimer' would likely run longer than 'Interstellar', at 169 minutes, and 'The Dark Knight Rises', at 165 minutes. 'Oppenheimer', which opens in theatres July 21, is Nolan's first movie at Universal Pictures after his long run at Warner Bros. It's based on Kai Bird's novel, 'American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer', and focuses on Oppenheimer's research effort as the Los Alamos Laboratory director. /IANS