There is several libraries missing in dependencies. While libalut0 is
just missing, the needed library libopenscenegraph65 is not in debian
anymore. And without that library, flightgear will not even start.
There might be others like libopenthreads13 (which is also missing in
debian).
Only the very outdated sparc64/sh4/m68k flightgear depends on those (and
hence is uninstallable: it should probably be removed). amd64
flightgear depends on the current versions:
Architecture: amd64 (x86_64)
Foreign Architectures: i386
ii libopenal1 1:1.16.0-3
ii libopenscenegraph100v5 3.2.1-8
ii libopenthreads20 3.2.1-8
If your flightgear won't start, you have a different problem; please
post the exact error message, and if possible, a debugger backtrace.
