That’s according to the National Oceanic Atmospheric Administration, which said pilots reported radio interference across the United States between noon and 2PM ET on December 14th. The current solar cycle is stronger than expected, making disruptions like this more likely, but the NOAA forecasts an October 2024 peak, a year earlier than originally predicted. Anyway, here’s a NASA GIF of the eruption.
Good question! Scientists have estimated the solar flare that occurred prior to the Carrington event might have at around an X-45 (Elvidge et al, 2018). I believe that this was the first flare ever recorded, but as you mentioned, we obviously we didn’t have modern detectors back then for measurement.