Those "cast saws" you are referring to, would more than likely not work.  I use one frequently to cut bone.  One nice thing is that they will not cut tissue, so unlike what you see in the movies they will not whack a guys head off with blood spurting everywhere (although they will cut thru a skull pretty quickly).  They primarily operate by vibrating a blade, similar to a hacksaw blade, but with bigger teeth, in a back and forth type of motion.  The high frequency ossilation will cause the hard substance (ie, bone or cast) underneath to disentergrate beneath the teeth of the blade.  My guess is that on a structure such as the plane airframe it would just crush the glass or make an irregular cut.  The hacksaw or razor saw look like the best thing out there right now.
Just my two cents.