John T wrote:

What's the lightest known nuclear bomb weigh?Â*Â*"Nuclear"Â*asÂ*inÂ*"fission"
or "fusion", not merely "dirty" with radioactive material.

I don't know that it's true, of course, but I've read several times that the
old Soviet Union had managed to build "suitcase" bombs. Of course, that
addresses more volume than mass, but I'd guess that these would be designed
to weigh as little as possible.

Still, and aircraft would be a poor way to deliver a nuke into DC when cars,
vans, trucks, and USPS deliveries are all available alternatives. If there
were a serious interest in security, these would all be kept out.

- Andrew