The Dark Knight became the fastest movie in history to break the $400 million domestic sales mark on Monday, doing so in just 18 days. The Chrisopher Nolan-directed Batman pic just recorded its third straight weekend in the box office top spot, taking in an estimated $43.8 million. Knight still has a ways to go, however, before it closes in on the highest grossing film of all time: Titanic, which hauled in $601 million, holding the top spot for an astounding 15 straight weeks in 1998.