We would need to know what size or model plane you are asking about. They are located under the fuel cells, if they have them. Not all planes can dump fuel.
It's the fuel from the engines.
It makes the aircraft lighter, and minimizes the effect of an explosion if it crashed.
Upturned wingtips cause the plane to use fuel more efficiently.
Depends on the plane, from the biggest (Airbus A380) 276,800kg to a smaller plane (Boeing 737) 38,147kg, however this is only the empty weight you also have to factor in passengers, fuel and luggage.
The airline says the plane burns just 3.1 liters of fuel per passenger per 100 kilometers (a little more than three quarts of fuel per passenger every 60 miles).
for the new one eBay.com and the old Lego passenger plane amazon.com
The worlds smallest passenger plane is probably a piper jet
Depends on the amount of fuel. Every plane has a different maximum landing weight. Fuel is very heavy stuff - usually almost half a jet's weight on takeoff. Commercial flights are calculated so that by the time the jet gets to its destination, its weight has been reduced by the burning of this fuel, and it is perfectly safe to land. In an emergency, though, if an incident happens just after takeoff, a plane may have to make a fast return to its departure airport. However, it is still full of the fuel for its planned flight, and therefore over its max landing weight. If the plane is still flyable, the pilot will perform multiple spiralling descending circles, burning as much fuel as possible until it is safe to land. The pilot can also physically open the fuel tanks and dump his fuel out the back.
The airbus A380 is the biggest passenger plane. It can hold 650 passengers.
It will take A while, Like maybe, 5 minutes,,,, But it would more likely evaporate into the air before it reached the ground. that would probably depend on how fast the plane is going
It is possible to dump fuel from some commercial aircraft. This is only done during emergency procedures to get the aircraft under a safe landing weight. The brown spots are not jet fuel, airline would not dump fuel unless it was a definite emergency. As we all know fuel is expensive and airlines cannot afford to just dump the fuel. The spots are possibly acid rain or tree particulate. If this is something that you must solve, I would look for a more simple answer.
Yes, airline staff can verify if a passenger has boarded the plane by checking the passenger manifest or using electronic boarding systems.