Airlines’ revenue from ancillary fees, primarily for baggage and reservation changes, will grow by 11.3 percent this year to $36.1 billion worldwide, a pair of consulting firms said Monday. The estimate by IdeaWorksCompany, of Shorewood, Wis., and Amadeus, of Madrid, Spain, suggests that the world’s airlines are swiftly catching up with U.S. airlines, which shifted toward such surcharges a decade ago, the Triangle Business Report wrote. U.S. carriers are on track to collect nearly $6.1 billion in fees for baggage and reservation changes, a 5.5 percent increase from 2011, according to an analysis of U.S. Transportation Department data. That represented growth of 5.5 percent from 2011, less than half the rate of global growth.