Passengers on Las Vegas-based Allegiant Air could have the choice on betting that fuel prices won’t rise. The airline is considering a plan where passengers can either pay a fixed fare, or a discounted price that rises and falls based on the cost of aviation fuel. If fuel rises between the time of purchase and the date of the flight, the passenger would pay the difference. But if fuel prices fall, there would be a discount. The “Review-Journal” says Allegiant’s chairman outlined the plan to the Department of Transportation, in response to possible airfare disclosure rules.