Terrorist attacks increase the funding of the intel and security institutions, so they have a vested interest in them occurring (and a state willing to kill tens of thousands of civilians in Iraq to advance its objectives likely has little problem sacrificing the odd planeload of its own citizens to maintain public support for its ambitions).
http://en.wikipedia.org/wiki/Umar_Farouk_Abdulmutallab#The_a...
Terrorist attacks increase the funding of the intel and security institutions, so they have a vested interest in them occurring (and a state willing to kill tens of thousands of civilians in Iraq to advance its objectives likely has little problem sacrificing the odd planeload of its own citizens to maintain public support for its ambitions).