I was on a NW flight last December DTW-NRT that had a medical emergency about 1 hour into the flight. We had to dump all of that fuel, land, fill up and head out again about 5 hours late. Spent about 20 hours on that plane instead of the 12 planned. Not fun.

The medical emergency was a diabetic who went into shock but was able to walk off by the time we landed. He looked pretty sheepish after causing the problem.