Just caught the tail end of a programme on Channel 5, Big, Bigger Biggest which looks at some of the largest engineering feats in the world. The bit I saw was about the baggage handling system for Terminal 5, which had to be tested with 12000 bags to be sure that it worked properly. It reminded me a little of the scene in ToyStory where the toys are on the high speed conveyor belt (they have early storage for check in bags and then the slow belts deposit the bags into trolleys which go at up to 30kmph to the planes. Lots of interesting design challenges in there. The programme cited a terminal in the US where the baggage handling did not work, bags kept falling off and it put the terminal out of action for a year while they fixed it.