What if they had say 12 or so guys willing to die, arranged in cells of three around the country, then they isolated and infected 1 individual from each group in some safe house, with smallpox, and waited for them to get sick. The other 2 guys of the cells could then use their human guinea pigs as an infection source and spread the virus laden pus over a wide area, hell, if they use one carrier/guinea pig from each group (keeping the other fresh and unexposed) then when the first gets sick replace him with a fresh (and formerly uninfected) carrier/guinea pig, the only limitation to its spread (aside from vaccine, or getting caught) would be enough idiots/"martyrs", and the quarenteening of an area.
If you had enough of these *ssholes spread around the country, do you think it would work?
Yea, I have no doubt. But the epidemology of the disease is such that there would have to be a lot of close contact with a large amount of people. And while hijacking a jetliner and crashing it into a building has a kind of terrible sexiness to it, slowly dying of a painfully disfiguring disease mighthave its problems finding volunteers.
The more likely route of infection is delivering the virus itself from some sort of device in a closed area frequented by many people (the example of an exploding light bulb in a subway was used).