An American Airlines Airbus A321-200, registration N150UW performing flight AA-2098 from Las Vegas,NV to Dallas Ft. Worth,TX (USA), was climbing out of Las Vegas when passengers detected smoke and haze in the cabin, the observations prompting the flight crew to stop the climb at about FL190 and return to Las Vegas for a safe landing on runway 25R about 25 minutes after departure. A passenger reported that flight attendants hinted that a recirculation fan had emitted popping noises, quit working heating up and emitted smoke. A replacement Airbus A321-200 registration N542UW reached Dallas with a delay of 4.5 hours.