I have been flying 747's for 20 years. If United 959 is referring to fuel dumping in stating that there is "SOME danger" let me reassure you that there is no danger in fuel dumping as the airplane is running at 100% as it was designed to do so. That is because it is designed to dump fuel.We practice dumping all the time in the simulator.
Airplanes are designed to takeoff above the maximum landing weight, when you land at your destination, you will be landing below your maximum landing weight because you have burned off your fuel going to your destination. For whatever reason you have to land right after taking off or before your destination due to- lets say a passenger who has a heart attack, you MAY have to dump fuel to ensure landing below the maximum landing weight.It is a simple straight forward procedure.
If there is any danger, it is because of something else. Not the fuel dumping. And if there was any danger, then there would be no fuel dumping because you would want to get on the ground as soon as possible. In this case, you MAY land overweight, but the airplane is designed to do this as well, but not on a normal basis. In this case this case , we will write in the maintenance log that an overweight landing was done so the maintenance people can do an overweight landing check to ensure that nothing was overstressed in the landing.
So if fuel dumping has to be done, you can be assured that there is no danger otherwise a landing would be done asap without fuel dumping.And if you return or land early for whatever reason, without fuel dumping, please don't think it is because there is danger- it is simply because we will be landing below the maximum landing weight at that time. If there is danger, at any time,you will know about it as the Captain will tell you and the Flight Attendants will prepare the cabin for an EMRGENCY landing. That happens when there is a dangerous or time critical situation.
Normally, at our company, the minimum altitude for fuel dumping is 4000 feet above ground. This ensures that the fuel is vaporized before it hits the ground.