Zero, barring any kind of civilization-ending event. There is no conceivable way we run out of every possible fuel option. In fact, just last year Airbus compl

Zero, barring any kind of civilization-ending event. There is no conceivable way we run out of every possible fuel option. In fact, just last year Airbus completed a flight with their A380 (2nd largest passenger jet in the world) using only biofuels.