Just like after 9/11, the airspace of an entire region is closed today, grounding thousands of flights in the UK and Northern Europe.
Unlike on 9/11, this time around the closure is not the result of the panicked, knee-jerk reaction of clueless politicians and officials. It is the result of a volcanic eruption in Iceland:
The plume, clearly visible in this Eumetsat image, is a grave threat to aviation. 28 years ago, volcanic ash almost brought down a British Airways 747 full of passengers, and since then, numerous airliners have been damaged as they flew through similar plumes. Grounding all flights in the affected areas seems like a dramatic, but justified response to a very real threat.
Now the question is this: how long? According to news reports, the eruption shows no signs of abating. Will they keep flights grounded for days, even weeks if necessary?