The highly anisotropic distribution and apparent alignment of the Galactic satellites in polar great planes begs the question how common such distributions are .
The satellite system of M31 is the only nearby system for which we currently have sufficiently accurate distances to study the three-dimensional satellite distribution .
We present the spatial distribution of the 15 presently known M31 companions in a coordinate system that is centered on M 31 and aligned with its disk .
Through a detailed statistical analysis we show that the full satellite sample describes a plane that is inclined by -56 \arcdeg with respect to the poles of M31 and that has an r.m.s .
height of 100 kpc .
With 88 % the statistical significance of this plane is low and it is unlikely to have a physical meaning .
We note that the great stellar stream found near Andromeda is inclined to this plane by 7 \arcdeg .
Most of the M31 satellites are found within < \pm 40 \arcdeg of M31 ’ s disk , i.e. , there is little evidence for a Holmberg effect .
If we confine our analysis to early-type dwarfs , we find a best-fit polar plane within 5 \arcdeg to 7 \arcdeg from the pole of M31 .
This polar great plane has a statistical significance of 99.3 % and includes all dSphs ( except for And II ) , M32 , NGC 147 , and PegDIG .
The r.m.s .
distance of these galaxies from the polar plane is 16 kpc .
The nearby spiral M33 has a distance of only \sim 3 kpc from this plane , which points toward the M81 group .
We discuss the anisotropic distribution of M31 ’ s early-type companions in the framework of three scenarios , namely as remnants of the break-up of a larger progenitor , as tracer of a prolate dark matter halo , and as tracer of collapse along large-scale filaments .
The first scenario requires that the break-up must have occurred at very early times and that the dwarfs continued to form stars thereafter to account for their stellar population content and luminosity-metallicity relation .
The third scenario seems to be plausible especially when considering the apparent alignment of our potential satellite filament with several nearby groups .
The current data do not permit us to rule out any of the scenarios .
Orbit information is needed to test the physical reality of the polar plane and of the different scenarios in more detail .