The rain in planes

SINCE people are made largely of water, transporting 350 of them thousands of kilometres through the air in a metal canister is a sweaty business. On average, each person on board a commercial airliner gives off 100ml of moisture every hour. That means a jumbo collects some 600 litres during a 17-hour transpacific flight, much of it as condensation in the gap between the cold outer skin of the aircraft and the insulated cabin wall. Meanwhile, the people who have sweated off this moisture are being tortured by a cabin atmosphere that is too dry. Its relative humidity is around 20%. Comfort demands a figure nearer 40%.