IMO, the best place to use 4-500s is on the ORD - LAX route. True, at 1,745 miles you are spotting UA to a certain extent, but Flight 121 is a 3:00 P.M. flight that is on a 3-class 777, so you upgrade to an int'l business class seat. I always use my E-500s on this route since I seem to have little luck anywhere else.