The total carbon emissions for a flight from London, United Kingdom to New York, New York is 1,300 lbs CO2.
This is equivalent to 590 kg CO2e or 0.59 tonnes of carbon dioxide equivalents.
With radiative forcing in effect, the carbon emissions may increase by 2.7 times, so the CO2 equivalents would then be 3,511 pounds, equivalent to 1,592 kilograms or 1.59 metric tonnes.
These calculations are based on the distance from London, United Kingdom to New York, NY which is 3,471 miles or 5,585 kilometers.
This trip is a long haul international flight. The calculation includes an assumption of a 79.7% load factor with 346 seats on the B747-400 and 261 seats on the B767-300ER.