Airports and ATC relied on power generators during the blackout. There were some delays but other than that it was business as usual.
We are somehow used to smaller power shortages, which are less common these days but used to happen once every few months until some years ago. Hospitals, emergency services, etc. all have generators and as far as I know there were no casualties related to the blackout. There were a few minor traffic accidents in Buenos Aires, though, as all traffic lights went out of service and it was raining.
When I woke up yesterday and saw on the phone that the whole country was off-grid I thought it would take several days to recover, but overall at home in Recoleta we were without power for 5 hours so it wasn’t that bad.
Tierra del Fuego was the only province which remained with power during the blackout. A side effect of being an island, they are not connected to the national electricity grid.