Among scientists, there is still an ongoing debate.
Aerosolized transmission happens - when an infected person expels microscopic infectious particles so tiny that they linger in the air and spread from person to person in air currents.
Certainly airborne transmission should have been more closely examined sooner during the outset of the coronavirus pandemic.
Simply by being indoors and rebreathing the same vapor-laden air molecules expelled by another person can be seen as a likely cause for transmission. Being outdoors lowers the concentration of any possible viral material you could possibly breathe in.
Link to article: Can air conditioners spread COVID-19?