Hi wizofoz,
I've enjoyed following your discussions over the last few days.
GENERAL relativity is applicable at any speed.
True - but Newtonian physics is a good approximation to GR and is much simpler to handle mathematically. GR can explain the advance of the perihelion of Mercury's orbit (1 degree per Century? something of that tiny magnitude)
Do we really need that sort of precision when discussing forces on an aircraft in the climb, or turning when pulling "delta g"? We know what earth's gravity feels like, so if we measure anything different - then it's due to some other acceleration.