It's completely within our technology to generate jet fuel in a carbon negative way (bringing it back to neutral after burning). Actually there are multiple methods to do it. They all cost more, especially because they're in small-batch proof of concept mode. Scaled up they would likely cost just a little bit more than our current fuel costs; but I view this as a completely valid way of folding in externality costs back into alignment with the direct economic activity of air travel.

Social investment (via government or other channels) into accelerating developments like this is why people need to get political to shift how the default decisions get made.