The plan is to use the extra 777s on MIA-EZE, which will likely remain two 777s this summer instead of 772/763 like it usually is during the Argentine winter. MIA-EZE is one of the few routes that AA has no problem getting full-fare F passengers. AA is also planning on adding a third daily MIA-EZE flight for winter '06, though MIA-EZE will still likely see two 772s and one 763s. The new flight will be a daylight service, and will not need any additional aircraft. So instead of spending the day on the tarmac at EZE, the redeye 777 that does MIA-EZE will do the daylight EZE-MIA, increasing utlization. The problem is that premium cabins have a harder time filling on daylights, so it is not for certain if the daylight will be a 772.
Also, RDU-LGW is a 777 because the route is subsidized by GlaxoSmith Kline and the subsidies pay for the F seats.