Hansen's notable work for "Dateline" includes coverage of the Columbine massacre, the Oklahoma City terrorist attack, the Unabomber and the TWA Flight 800 disaster; as well as investigative reports on Indian child slave labor and on counterfeit prescription drug sales in China. Hansen was responsible for most of "Dateline's" coverage of the 9/11 terrorist attacks, as well as stories on terrorist groups and the operations of Al-Qaeda. He exposed how a group linked to Osama Bin Laden had tried to buy missiles and nuclear weapons components, and he also worked on an exclusive report detailing an attempted 1994 terrorist attack in France. His series on the lack of security at airports resulted in the Federal Aviation Administration opening an investigation and ultimately revising its policies.