Howto have thunderbird/lightning open ics files

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http://askubuntu.com – Some websites offer .ics files, calendar files. I would like thunrbird to open these with Lightning so it can add the events in the ics-file to its calendar. When I use /usr/bin/thunderbird to open the file with, it starts a new message with the ics file attached. I could download the file, then import it from lightning, But I rather have lightning just open the file. Is there a commandline-option for this? Some wrapper-script maybe? Should I change something in firefox? (HowTos)