Covid-19 a bioweapon?

Covid-19 cannot be a bioweapon since it is not airborne.

This is a claim. Must bioweapons  be airborne? To my knowledge and standard definitions that come up when Googling, no. So it appears to be a false claim.

If a country will make a bioweapon, why not make the same as transmissible via air which makes it a more effective and dangerous weapon?

This is a reasonable question. But since I am not a biochemist nor a psychopathic mass murder, I don't have an answer.

Coronavirus is not airborne in the same sense as a bioweapon is artificially engineered to be ("weaponizing"), which is a kind of ambiguity that adds difficulty to the discussion imo.

Afaik, coronavirus is conventionally airborne, transmitted by cough that briefly aerosolizes sputum with the virus, but if this were an intentional thing, it would be depending on the concept of "going viral" as if it were a video.  Might make a good horror story, but hope is not a basis for planning.

I also think "why not" is "what if", perhaps along with a fallacy of appeal to perfection. that it can't be a bioweapon because "they" would have made a better one. Might be true, but it's a weak argument imo.

Restating the above as a deductive argument:

Major Premise: Bioweapons must be airborne

Minor Premise: Covid-19 is not airborne.

Conclusion: Therefore, Covid-19  cannot be a bioweapon. 

Analysis: Covid-19  IS airborne, so the Minor Premise is factually false. This makes the argument UNSOUND. (Note that this is a VALID argument nonetheless because the conclusion follows from the premises. And, to be precise, it is the coronavirus that is airborne; Covid-19 is the disease caused by the virus.)

I would say it might be a Non Sequitur Fallacy, but the conclusion does follow the premise. Its just that since the premise is false, so is the conclusion. 

All bioweapons must be airborne. (False premise)

COVID-19 is not airborne. (False premise)

Therefore COVID-19 is not a bioweapon. (False conclusion, based on false premises)

Its a false premise, because bioweapons don't have to be airborne, and COVID-19 is airborne in the sense that it can survive up to 3hrs in the air in micro-droplets.