China Southern has recently figured out that since it takes a liter of fuel to flush a toilet in-flight, passengers are recommended to use the bathroom prior to boarding the plane. That, according to a China Southern captain, is enough for "an economical car to run at least 10 kilometers".
The captain, Liu Zhiyuan, also said that flying around one kilogram of items like pillows, blankets and magazine for one hour consumes 0.2 kg of fuel, meaning that "the blankets and pillows on board the aircraft eat up 60 tons of fuel every day. If each seat is loaded with three 450-gram magazines, another 60 tonnes will be consumed," he explained. Apparently the airline is also filling their on-board water tanks at 60 percent full.
I'm surprised good old Ryanair, which doesn't have any window shades, pillows, etc., hasn't told its passengers use the bathroom before boarding.