Airports that float on water. I know what you're thinking, 'Cool idea, Jonathan, but that will never actually happen!' Well maybe... but maybe not! Floating airports would solve some major problems that plague their land-bound cousins, offering virtually unlimited runway expansion to cities with very limited land area. Recently we've seen some serious efforts to turn floating airports into reality. From the experimental mega-float project in Japan, to the proposed London Britannia Airport in the Thames Estuary, today we're looking at the crazy engineering ideas that could be the future of airports.