Delta Air Lines Inc. fell the most in almost two months after it lowered forecasts for some third-quarter targets, pushing other U.S.-based carriers lower.

Delta slid as much as 5.5 percent, its biggest intraday decline since July 8. The shares were trading at $39.01 at 10:54 a.m. in New York, down 4.7 percent. The Bloomberg U.S. Airlines Index fell 2.7 percent.

In a presentation to analysts at a Cowen & Co. conference, Delta said revenue for each seat flown a mile will increase 2 percent to 3 percent in the third quarter, down from a previous forecast of 2 percent to 4 percent. The Atlanta-based carrier also lowered its September-quarter operating margin to 15 percent to 16 percent from a 15 percent to 17 percent range in July.

“They just took the high end down,” Michael Derchin, an analyst at CRT Capital Group in Stamford, Connecticut, said in an interview. “It doesn’t mean they won’t make the high end.”

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Photo Credit: A Delta plane in Salt Lake City, UT. Aero Icarus / Flickr