We've already discussed the fact that the flights of Air Force One are conducted by the military. All the funding for the United States military comes from the public purse. That means taxpayers are covering the costs of the flights.
As a minimum, each time Air Force One takes to the sky, the American taxpayer takes a $200,000 hit. Nobody ever said that diplomacy came cheaply - and neither does jet plane fuel or the salaries of great military minds!