The triple-7 from BA who crash-landed at Heathrow had only about 10 tons of fuel in the tanks. Is this normal?

Question

I mean, normally, you must have at least fuel for 30 minutes in the holding, and then enough fuel to go to the alternate. But would the B777 have had really enough fuel for this, with just 10 tons left after the "normal" trip?

(And besides that, normally, even after burning the contingency fuel to go to the alternate and making some holdings, you are not allowed (from the administrations) to land with less than 4 tons. So in the worst case, you must have 4 tons minimum of fuel to land.)

Answer 1

10 tons was plenty. typically they land with 6-8 tons remaining.

Answer 2

Let's try a reasonableness approach.

10 tons of fuel is 20,000 pounds. Jet fuel weighs around 6 pounds per gallon making about 3300 gallons of fuel. The engines of a 777 use 14.4 gallons of fuel per minute each. That is a total flying time remaining of 114 minutes. If, as you say they must land with a minimum of 4 tons, then there was still a discretionary flying time remaining of 68 minutes.

Does that seem reasonable or unreasonable?