Yes, this all sounds like a complicated way to say "obviously we've got to reduce air travel, but I'm not going to fly less, because what can one person do".

This should be a named fallacy.

Works in all sorts of situations: "obviously I have to eat less, but not this mealtime".

There is a difference between decision making and calculations of change.

I am certainly not arguing that decisions shouldn't be made responsibly. I am merely trying to point out that the calculations that have been made are simplistic.

That is certainly true, but from the scale of the calculations, I am assuming that ecopassenger.com is not just calculating that difference, but the overall emmission cost as a ratio of flight.