The principles involved here are not dependent on spaceflight or any new technology, but apply with current technology just as much. In fact, almost twelve and a half years ago, terrorists actually did this exact thing, but with airplanes rather than spaceships.
From this, we can try to extrapolate to the possibility of this happening on a larger scale. So I have two points: The first is that that attack was by far the largest and most destructive terrorist attack ever. If it involved spaceships rather than airplanes, it would have been even larger and more devastating. The second is that since then, not a single attack has managed to get even close to that one in devastation. Modern security measures against attacks like that one seem to be working, and that shows that effective measures against attacks like this are possible.
Modern security measures like fellow passengers not accepting the line that they're hostages, instead fighting vigorously.
The air would already have been safe on September 12, if anything had been in the air by then.
A reality of physics, and one that doesn't get much play in science fiction, is that as soon as humanity gains space travel, anyone in the asteroid mining or space travel business will have city-busting capabilities at their fingertips.
It's there in classic sci-fi, but not so much recently.
This discussion was started in the comments to:
http://lesswrong.com/lw/gln/a_brief_history_of_ethically_concerned_scientists/
In the "Ethically Concerned Scientists" post, Izeinwinter commented:
A great start to a discussion here.
You've considered people going loons and some general security, but it would then become a hacker war along the lines of who could break the security and gain control of the space ships.
It doesn't address the problem of the leaders using the ships as threat weapons, since they have legitimate control, but can still make terrorist decisions.
And I'm terrified of your idea of turning spaceflight, which I see as the ultimate freedom, along the lines of Niven's Belters, into a state-controlled affair like the Soviet navy with political officers.
Now, one thing I think is a useful safety control that doesn't lead to worse problems is the destruct option. All major rockets have them right now, since if it goes out of control it's a huge hazard for a great distance. And although I don't like the idea of all personal spaceships being under a safety officers thumb, it might be better than the alternative of terrorist groups gaining control of asteroid mines and holding the world hostage.
You're right about great story potential though, in any of these scenarios.