I have tested on Mac OS X 10.9.5, tried to update to Adobe AIR 19.0.0.241 from Adobe AIR 19.0.0.213 with the following command and I was still getting the same error when no users are logged in locally:
# sudo launchctl bsexec $(ps aux | grep [l]oginwindow | awk '{ print $2 }') "/Volumes/Adobe AIR Installer.app/Contents/MacOS/Adobe AIR Installer" -silent -eulaAccepted
_RegisterApplication(), FAILED TO establish the default connection to the WindowServer, _CGSDefaultConnection() is NULL.
Any command might work? Do you have any update on this issue?
-TeamOCD