Alaska Air Group Inc. ALK revised its third-quarter guidance on Wednesday, after a considerable increase in fuel costs in recent weeks. In a regulatory filing, the airline said it’s now expecting third-quarter economic fuel cost per gallon to be about $3.15 to $3.25, up from prior guidance of $2.70 to $2.80. It expects its adjusted pretax margin to be 10% to 12%, compared with prior guidance of 14% to 16%. The company is expecting its capacity to be up about 13%, compared with prior guidance of up 10% to 13%. Revenue is expected to be up 1% to 2%, compared with prior guidance of flat to up 3%, weighed down by the wildfires…