Notes:I have included a picture of the EHSI which shows that we had a 212 Knot tailwind. This is just abeam Lexington Kentucky. We were down at 29000 feet because the ride was pretty poor up high. Smooth as silk at 290 and nice tailwind! I bumped up the speed to Mach .83 to see what kind of groundspeed we would get. The FMC had us cruising at .74 with a Cost Index of 40 because of the high tailwind.