Thanks Bellerophon. Great thing about FT - someone's bound to have the answer.

As a matter of impression, I reckon that a 744 could carry a theoretical 17 hours' flying's worth of fuel. They fly plenty of 14+ hour sectors, block time. If you add some holding fuel, diversion fuel, more holding fuel, contingency fuel and the legal reserves which ought still to remain in the tanks after landing, that would be another couple of hours' worth of flying. Not that you could legally plan to operate the aircraft on a 17 hour sector, though.

That consumption rate for a 777 seems a bit low, though, comparing it to Bellerophon's figures.