I've never given much thought to what the airlines might claim to be the breakdown of the sum I pay for the flight because the fixed costs don't really define t

I've never given much thought to what the airlines might claim to be the breakdown of the sum I pay for the flight because the fixed costs don't really define the lump sum price anyway. Competition is fierce enough to drive down those costs over which airlines have any control at all. I think that for any route worth its salt the prices are close enough to what's actually sustainable for the airline and not necessarily that much higher. This is very different for more remote and less-used routes where one or two company might enjoy a geographical monopoly. The thing is that the airlines make sure there's always something you can buy from at a crazy prize. The classic example might be the first class ticket for the next departing flight. Even each first class and business seat allows the airline to give a small discount for all economy seats because people are willing to pay a different price for things they value differently. Further, because seats are sold one by one, even economy seats can cost double or half depending on when and how you're buying them. Personally, I book my flights somewhat in advance, picking a combination of flight times and prices that I find tolerable myself. The limits are all subjective and can change. But I don't care if I paid five dollars/euros/pounds more or less because of "passenger civil aviation security service fee" because the major factor for how much I end up paying is how the market works for airline tickets. If the fee was 2 pounds or 20 pounds, I might still be paying the same price. Or I could be paying a hundred pounds more (or less) for the ticket even if the fees would be a few dozens pounds less (or more).