Sure you can, but that means you're using additional coal just for the purpose of making jet fuel, adding additional CO2 to the balance. By using CO2 from exist

Sure you can, but that means you're using additional coal just for the purpose of making jet fuel, adding additional CO2 to the balance. By using CO2 from existing coal power plants you'll be CO2-neutral for the jet fuel. After all, if the point is to get fossil jet fuel it is even easier to use crude oil, of which there is plenty to go around. The Germans used the FT-process to get around the fact that they had coal of different types but only little oil, not because it is the easiest way to produce liquid hydrocarbons.