I did an ashes scattering a few years ago, from a C172. The nephew of the deceased had obtained a special urn from the crematorium with a removeable base and he hung the whole lot out of the window whilst I flew the aircraft and pulled the handle. We did get a bit blown back in but not much. I simply shook the floor carpet out on the grass when we landed for fuel...and yes it was simple to get permission and it is the one relaxation from the ANO prohibition on dropping of articles that is FREE!