(Anonymous)
After more thought - flying is also kind of an extension of LeviCorpus (only upright) but applied to oneself instead of to someone else - that also might have given Snape a place to begin? And we have a pretty good idea that the DEs in Bk4 use Snape's LeviCorpus spell at the World Cup on the Muggles. Presumably, they learned it from Snape - either back when they were students or soon after they became DEs.
But I also think that IF Snape did invent the 'flying' spell, then he would HAVE to hand it over to Voldy - just in case Snape ever DID need to use it himself. IF he did, then it wouldn't be very good to need to explain to Voldy just why he never 'shared'. So IF he invented it earlier, then he doesn't need to share it until after he killed Albus, when he knows he will suddenly be one of the DEs going out on raids (and just MIGHT get knocked off a broom)
Therefore IF Snape taught it to Voldy, then I think it happens between Bk 6 & 7.
PS - watch out for those sharp plot-bunny fangs! They can cut deep! -- Hwyla
But I also think that IF Snape did invent the 'flying' spell, then he would HAVE to hand it over to Voldy - just in case Snape ever DID need to use it himself. IF he did, then it wouldn't be very good to need to explain to Voldy just why he never 'shared'. So IF he invented it earlier, then he doesn't need to share it until after he killed Albus, when he knows he will suddenly be one of the DEs going out on raids (and just MIGHT get knocked off a broom)
Therefore IF Snape taught it to Voldy, then I think it happens between Bk 6 & 7.
PS - watch out for those sharp plot-bunny fangs! They can cut deep! -- Hwyla