Fuel Jettison: Raining Kerosene
The quick fuel draining system (called Fuel Jettison) is an onboard system in large aircrafts like B747, B767, B777 and some B757 and also A330 and A340.
When an emergency procedure around an airport is carried out, the airplane must be able to land with the Take Off Weight (sometimes Maximum Take Off Weight). Then, the low/mid range airplanes have no problems dealing with that, but long range airplanes does. Heavy airplanes usually carry a huge amount of fuel (because of long haul flights). Thence, according to JAR regulation JAR 25.1001 about Airworthiness, these heavy aircrafts must be equipped with a Fuel Jettison system. The regulation require to the system to empty the tanks in 15 minuts, and then leaving enough fuel to keep a 3.2% climb gradient in landing configuration at 1.15 stall speed. For example, a B727 releases 1060 kg (2330 lbs) of fuel per minute, with all tank pumps running. The fuel nozzle is set at the wing tip, in order not to make any damage at the airplane fuselage.
Source: Wikimedia
Even though this procedure seems pretty enviromentally harmful, it isn’t much critisized because its low frequency, low amount of sprayed fuel and the procedure conditions. If possible, fuel jettison procedure must be done over the sea.
Crossing the Skies 
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