you read the manual ?
this one in the ftp archive
http://mirrors.ibiblio.org/flightgear/ftp/Docs/
see chapter 2 page 19 of the pdf
section 2.1 " installing scenery "
there is something very odd with the photo in the first post
the folder
"/usr/share/games/flightgear/scenery "
has the root "/" folders in it
/bin,/boot,/lib,/usr/ ,/var should not be in the scenery folder
and if that is the / that is displayed then the flight gear data should not be being extracted to "/"
on a debain / ubuntu based os like mint
what did you install for the main flightgear program
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Ubuntu: Option 1: FlightGear v2.10 packages are now available from PlayDeb.net
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Ubuntu: Option 2: On Ubuntu, FlightGear can be installed using the “synaptic” tool.
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Ubuntu: Option 3: Launchpad PPA for FlightGear 2.10 (contributed by Saikrishna Arcot)