A Lancet Comment lists some scientific reasons why airborne transmission of SARS-CoV-2 is likely. Here is the brief summary of those reasons:
1. The high incidence of super-spreading events suggests the dominance of aerosol transmission;
2. Long-range transmission of SARS-CoV-2 between separated people in adjacent rooms has been documented;
3. At least a third of SARS-CoV-2 infections occurs without involving a coughing or sneezing patients;
4. Higher infection rate occurs indoors than outdoors;
5. Healthcare workers are infected even though wearing personal protective equipment to protect against droplet.
More reasons can be found on the original webpage: