Fighter jets burn through fuel at an exorbitant cost. I have the solution.. CHARGE ADMISSION. People WILL pay to go to an airshow. They are hardcore fans and usually repeat customers (This also keeps the riffraff out). Charge admission, with funds covering fuel costs. Done.
Airshows can easily get tens of thousands of people showing up. Most people would have no problem paying a small entry fee to offset some of the costs.