1000kgs, sounds a lot to some people, when in fact for a mid size jet (757) it is about 4 times round a holding pattern. That is not an unusual practice at some high traffic density airports. Carrying a tonne of fuel extra costs approximetaly 4% of its own weight per hour (40kg or 50 litres per hour) that would mean a rough cost figure of about £18 (US$33) for a 1 hour cruise flight, £ 54 (US$99) for a 3 hour flight. Compare that to the cost of a diversion.