Basically the proposition is that aero's should be able to move on the vertical diagonals. Basically banking ascents and descents.
It would turn fly commands that are pretty common, like
fly up up up up up up n n n n n up up n n e se
A route that to graph looks a bit like this.
a chained movement of 19 moves into.
fly upn upn upn upn upn upn upn upe se
A graph that probably looks a bit like this.
A chained movement of 9 moves.
The performance benefits could be rather decent as well, as flying fast tends to lag the server like a motherfucker, and less moves would probably mean less lag overall on the server side.