[Nowhere Man]

The full weight of a 767 doesn't even come close to 500,000 tons, let alone the fuel load. In fact, the maximum takeoff weight of a 767 is 450,000 POUNDS, with the fuel capacity of 23,980 gallons. (.5Kt is 1 mega pounds) JP4 is pretty wimpy compared to TNT. That report was super duper wrong.

I don't know, when you have a large quantity of jet fuel being spread out as the result of the impact, you have something like a fuel/air bomb and I think they could be taking that into account. I know there are some fuel/air bombs that can rival a small nuke. I know a couple of months ago, a house about a mile from me exploded due to natural gas and I felt the shockwave hit my house, I remember my mother wasking what is was and I had no idea until I heard it over the news and on my police scanner. I guess maybe half a kiloton might be a little much, maybe not.

[antidisestablishment]

Try this for a more realistic analysis:

Conclusion

... Without additional data, it is impossible to say with an acceptable level of certainty whether any number of these weapons was stolen during and following the breakup of the Soviet Union, as Alexander Lebed and a few other Russians claimed.

Available evidence suggests that these stories were most probably not true, and that they were generated by incomplete information or ulterior motives. The probability that such weapons could be used by terrorists (assuming some were stolen) appears even lower.