United Airlines CEO Scott Kirby is warning travelers that rising jet fuel costs could soon hit airline ticket prices. “No one hedges anymore, and even if you do, hedging the crack spread is really hard to do,” Kirby said during a recent event at Harvard University. “Airfare increases will probably start quick” as higher fuel costs ripple through the airline industry. The crack spread is the difference between the price of crude oil and the price of the fuels made from it, like gasoline or jet