<Here's an article on the dangers of plane impact with nuclear containment buildings. Granted, it's an anti-nuke site, but there is no reason to doubt their analysis of the GE study. As the crew member of the "Death Star" said in "Star Wars:" "We've analyzed their attack, sir, and there is a danger."

Of course, the blatantly obvious solution is a simple WW II-type network of barrage balloons around the containment building at the proper distances. Barrage balloon technology was relatively mature decades ago, and would be very inexpensive.

Nuclear reactors would be superbly suited to this defense. As targets, they are highly localized, often in relatively rural areas, requiring a minimum number of balloons. They are not very tall (at least compared to a skyscraper) so that like the Pentagon attack, an attacking plane would be forced to approach at very low altitude and a very shallow angle of attack. The only alternative to avoid the balloons, diving a large, loaded commercial plane at a very high negative angle of attack, and then hitting an object the size of a containment building, would be an extremely difficult task (assuming the plane held up to the maneuver at all.)

As a passive defense, it would not require the constant vigilance and decisions required of an active defense, like anti-aircraft missiles.

The only problem might be if there is a large reactor located in the flight path of an airport, but for obvious reasons I do not believe a reactor has ever been built along an approach.

One of the problems with barrage balloons in warfare was that they obviously identified the location of a valuable target. However, the locations of American reactors are anything but secret, so this is not a factor.

Such balloons might also be used to defend other targets, but I doubt that modern folks would be as tolerant of these things over cities as Londoners were, especially now that cities contain commercial airports. Then again...who knows?

WWII Barrage Balloon mobile deployment force. "In Silence We Serve."