Delta Air Lines cut its passenger unit revenue and operating margin outlook Tuesday for Q3, citing higher fuel prices and a "slower than anticipated" rebound in its domestic pricing power on flights booked closer to their departure. Delta's forecast for unit revenue comes some 2 months after several carriers signalled a weaker showing for the key metric and more fare discounting in some parts of the US this quarter. More competition is one reason: JetBlue said last month that it would double flights into Atlanta. Iceland's WOW carrier said in August that it will expand super-discount trans-Atlantic flights to more US cities. Delta expects Q3 unit revenue to be up 2%-3%, compared to an earlier outlook for 2.5%-4.5% growth. Operating margins for Q3 are expected to be 16.5%-17.5%, lower than previous expectations for 18%-20%. <br/>