BTW, flying level at a safe altitude doesn't seem to be of much help: http://www.youtube.com/watch?v=aHJOpHryjfE&feature=related
I have no confidence that the voices we hear are the original voices from that clip. Could quite easily be edited later to make the Peruvians look entirely responsible.
You will notice that some voices sound crackly like a normal aviation radio does, where as others sound very clear. It's not proof, just a thing to think about.
Ironic that it was christian missionaries though. Almost slighty funny. But, sorry, tragic more than anything, I know.