(Reuters) -Southwest Airlines ( LUV ) on Wednesday lowered its second-quarter forecast for revenue per available seat miles (RASM), a proxy for pricing power, citing uneven travel demand, sending its shares down 9% in premarket trading.

The company said changing travel patterns meant it was unable to sell the amount of seats it wanted to.

The carrier now expects current quarter RASM to be down between 4% to 4.5%, compared with its previous estimate of a fall of 1.5% to 3.5%.