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from bbc.co.uk article:
http://news.bbc.co.uk/hi/english/uk/...00/2083660.stm
Research by aircraft maker Boeing found that if economy seats in its 777 airliner were arranged with three by each window and three in the centre, the flight would have to be two-thirds full before passengers had to seated beside one another.
While Boeing recommends this 3-3-3 configurations, many airlines operate a 2-5-2 system almost guaranteeing you'll have a neighbour if half the seats have been sold.
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Can anyone suggest why on earth some carriers choose to configure their 777s in 2-5-2, instead of 3-3-3? Never understood this one....