https://www.pbs.org/wgbh/americanexperience/features/weapon-...
> "The first Large Area Concept experiment, in 1957, involved dispersing microorganisms over a swath from South Dakota to Minnesota; monitoring revealed that some of the particles eventually traveled some 1200 miles away. Further tests covered areas from Ohio to Texas and Michigan to Kansas. In the Army’s words, these experiments 'proved the feasibility of covering large areas of the country with [biological weapons] agents.'"
Well before airplane contrails were ever associated with a plot to alter the climate, it was all about a plot to control people's minds with toxic chemicals etc.
Of course, it is entirely true that a relatively small fleet of drones could disperse enough anthrax/smallpox powder over any large American city to cause mass casualties and initiate a pandemic-scale event, which is why development of such weapons is banned under the terms of the Biological Warfare Convention, although the Soviet Union violated that treaty on a massive scale in the 1970s and 1980s, and Israel and several other states have refused to sign it - and the US government has strongly opposed anything like an inspection / verification system, so...
Almost every 'conspiracy theory' has some seed of truth hidden inside it somewhere.