From page 2 of the discussion: "Anyway, back to some figues; at Mach 2, 50,000', the typical fuel burn per engine would be around 5 tonnes/hour, falling to around 4.2 tonnes/hour at 60,000'." So at 60,000 feet, total fuel flow would be: 4.2 tonnes/hour * 4 engines = 16.8 tonnes/hour 16.8 tonnes/hour * 326 gallons per tonne = 5477 gallons/hour 5477 gallons/hour * 1/1320mph = 4.15 gallons/mile, 0.24 miles/gallon 0.24 miles/gallon * 120 passengers = 28.8 passenger miles/gallon

The 787 boasts around 120 passenger miles per gallon. So the Concorde uses 4x this much at highest efficiency. Not bad for 60's engineering at mach 2! I can see why it was not profitable to operate however, due to the increases in fuel cost since the aircraft was designed.