How much do the fan blades of a GE90-115b stretch when the engine is spinning at maximum RPM?
I don't know the exact answer, but it's on the order of 0.100" (i.e. it's more than 0.010" and less than 1.00").  The more interesting part is that it's not just a simple linear stretching. The blades have a twist to them, and at speed they untwist, which is a strong contributor to the total change in length from 0 rpm to redline.