BERLIN - Growth in demand for air freight is slowing, as world trade growth weakens, a leading air industry body said on Thursday. Air cargo volumes rose 3.3 percent in April, compared with average growth of 5.3 percent over the first three months of the year, and only the Asia-Pacific and Middle East regions reported growth, IATA said in its regular monthly freight statistics. Capacity also increased 5.5 percent in April, pushing the load factors - a measure of how full planes are - down to 44.7 percent. “After a volatile start to 2015, the market is settling down, and it is clear that momentum in air freight growth is being lost,” IATA Director General Tony Tyler said in the statement.