By Dan Weil ‘We believe airlines are set up for positive revisions this summer, and we raise our estimates for second-quarter guidance,’ BofA said. In their first-quarter earnings reports, airlines offered strong forecasts for the rest of the year. Yet their shares have fallen recently, with the U.S. Global Jets ETF (JETS) – Get U.S. Global Jets ETF Report, sliding 13% since April 21. So what gives? “Last week, Delta Air (DAL) – Get Delta Air Lines Inc. Report, American Airlines (AAL) – Get American Airlines Group Inc. Report, Alaska Air (ALK) – Get Alaska Air Group Inc. Report and Hawaiian Ai…