All suggestions welcome … my system is down
root@piaware:/home/pi# apt-get update
Hit:1 http://www.flightaware.com/mirror/raspbian/raspbian buster InRelease
Hit:2 http://www.flightaware.com/adsb/piaware/files/packages buster InRelease
Get:3 http://www.flightaware.com/mirror/raspberrypi/debian buster InRelease
Err:2 http://www.flightaware.com/adsb/piaware/files/packages buster InRelease
The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY B931BB28DE85F0DD
Get:4 http://www.flightaware.com/mirror/raspberrypi/debian buster/main armhf Packages [400 kB]
Fetched 432 kB in 2s (232 kB/s)
Reading package lists… Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://www.flightaware.com/adsb/piaware/files/packages buster InRelease: The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY B931BB28DE85F0DD
W: Failed to fetch http://flightaware.com/adsb/piaware/files/packages/dists/buster/InRelease The following signatures couldn’t be verified because the public key is not available: NO_PUBKEY B931BB28DE85F0DD
W: Some index files failed to download. They have been ignored, or old ones used instead.