Airline seats, unless you can afford business class+, are a source of great discomfort. From a ticket buyer’s point of view, the major issue is a lack of room to wiggle one’s legs occasionally in transit (which can have health implications such as deep-vein thrombosis).
How about providing 16% more legroom (on average)? That’s the estimated decrease in seat utilisation across the US, since the onset of the current financial reality check.
Today’s invention is to make more use of the existing floor rails in airliners. A single, floor-level, catch (a little like one of those clamping tie-racks) would release a block of seats to slide, under the influence of springs between them. The fraction of unbooked ones would be pressed up against a bulkhead, leaving others free so that their interseat distance would be automatically equally distributed (and increased).
The catch would then be re-engaged, locking all seats in their new, more comfortable locations.
See also this:
http://news.bbc.co.uk/1/hi/magazine/8779388.stm