The cost of fuel seems to account for about 20% of the cost of the ticket on a US domestic flight (source). Given that international flights have higher fees, I expect the fuel cost percentage to be even smaller for them.
For example I took a look at a New York—London return economy ticket which costs about $1050 now. Out of that amount $250 are government taxes and fees (NOT including the sales tax).
The cost of fuel seems to account for about 20% of the cost of the ticket on a US domestic flight (source). Given that international flights have higher fees, I expect the fuel cost percentage to be even smaller for them.
For example I took a look at a New York—London return economy ticket which costs about $1050 now. Out of that amount $250 are government taxes and fees (NOT including the sales tax).