How much CO2 does a ton of aviation fuel produce?

A BBC news article on December 3 (http://news.bbc.co.uk/1/hi/england/7124021.stm) reports that a jet flying on a ‘tango route’ from Manchester to Tenerife would use an extra 1.6 tonnes of fuel compared with a direct flight, and that this would generate 3 tonnes more CO2. Please could a chemist explain to me how this works?

3/1.6 = 1.875 suggests that 1 tonne of fuel would generate 1.875 tonnes of CO2.

I don’t know the composition of aviation fuel, so I decided to approximate three times:
1C + O2 -> CO2
12g of C gives 44g of CO2.
1 tonne of C gives 3.666.. tonnes of CO2

2CH4 + 3O2 -> 2CO2 + 4H2O
32 g methane -> 88 g CO2
Then 1 tonne of methane gives 2.75 tonnes of CO2.

One tonne of aviation fuel will produce between 2.75 and 3.666 tonnes of carbon dioxide, if the fuel is completely burnt.

Best approximation here:
Benzene + O2 -> carbon dioxide and water
Simplified
6CH + 6.5 O2 -> 6CO2 + H2O
78 g benzene give 264 g CO2
1 tonne benzene will give 3.38 tonnes of carbon dioxide.

My results suggest that more CO2 is produced than in the report about the news report.

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