Related: Some airliners directly transmit automated weather reports via either AMDAR or AIREP.

AMDAR: https://madis-data.ncep.noaa.gov/MadisAircraftPublic/

AIREP: Go to https://www.1800wxbrief.com/Website/interactiveMap, turn on the "Pilot Reports" layer, and look for "ARP" symbols on the map. You'll mostly see these over oceanic routes, especially in the Atlantic.

The AIREP reports are coded in PIREP format, so you'll need to look up the instructions for manually decoding those online.