777-200 'planned' fuel burn equates to an average of 6 tonnes an hour in the cruise. Extra needs to be taken into account for climb and cruise climbs.
Minimum reserve fuel for our fleet 'tends' to be around 3 tonnes.
Taxi fuel, contingency fuel and diversion fuel on top.
For example a recent flight of mine, 10 and 1/2 hours.
Trip fuel 77.3 tonnes
Contingency 2 tonnes
Div 3 tonnes
Reserves 3 tonnes
Taxi 500kg
Total 85.8 tonnes.
Make of that what you will if you want to calculate how much fuel they would have had on board.
As a previous SAR pilot kerosene will show up as smooth 'rainbowing' on the surface of the sea. Crude oil produces the brown slicks and grey water discharges from merchant vessels.
My condolences to the crew and passengers, I will await the accident report with interest.