You can only pray that retaliatory action against countries harbouring the terrorists does not simply escalate into a near war between that state - and its allies - again the US and theirs. It seems that the US has to take action, but how on earth you prevent that turning into a bigger war, only God knows.
The US could drop that 'son of star wars' nonsense now that we can see how the very everyday things such as planes can cause such heartache and havoc if there's someone with enough determination to kill.
How vulnerable do those two towers seem now? Something so huge, so important to the US economy and so full of people just have to be prime targets. Maybe, in the future, important workplaces will be smaller and more underground, and not displayed as icons of wealth.