The attempted crashing of Tel Aviv-bound Flydubai Flight FZ1073 is the latest reminder of Islamist extremists' decades-long focus on civilian aviation. Al-Qaeda terrorists hijacked four American airliners on 9/11 and killed nearly 3,000 people. Months later, Al Qaeda member Richard Reid, who converted to Islam, attempted to destroy an American Airlines flight with explosives hidden in his shoes. In 2006, British authorities disrupted an Islamist plot to simultaneously destroy multiple transatlantic aircraft using liquid explosives. In 2009, al-Qaeda-trained Umar Farouk Abdulmutallab attempted to bomb Northwest Flight 253 as it approached Detroit with 290 people aboard. The threat has repeatedly crossed borders, airlines and continents: perpetrators have targeted American carriers, transatlantic routes and now a passenger jet flying to Israel. European and other Western governments cannot treat aviation terrorism as a threat confined to another country or another era. Islamist terrorism remains a transnational security threat capable of crossing borders and targeting civilians, transportation networks, and public spaces.