Sandra Bullock (Linda Schell) was in New York City with her family and witnessed the second plane, United Airlines Flight 175, crashing into the World Trade Center's South Tower on September 11, 2001.
James Gandolfini filmed scenes as someone who meets Sandra Bullock's character at a grief counseling, but they were cut from the film due to a negative test audience reaction. His character was mostly likely Ron from the book. Gandolfini's name still appears on promotional materials for the film, however.
Director Stephen Daldry hoped the film would be completed for the fall of 2011 so that it coincided with the tenth anniversary of the 9/11 attacks. It wasn't.
Max von Sydow turned down the role of Hal in Les débutants (2010) (eventually taken by Christopher Plummer.
Thomas Horn came to the attention of Stephen Daldry when, at the age of 12, he won $31,800 on a "Kids Week" episode of the television series Jeopardy! (1984) that aired July 8, 2010 (a date Thomas mentions at 00:44 in the special feature "Finding Oskar" on the Blu-ray disc).