Demand for air freight rose just 2.2 percent in 2015, down from the 5 percent growth seen in 2014, due to sluggish trade growth in Europe and Asia, the International Air Transport Association (IATA) said on Wednesday. “In 2011 air cargo revenue peaked at $67 billion. In 2016 we are not expecting revenue to exceed $51 billion,” IATA director general Tony Tyler said in a statement. The association said while the outlook for air freight and world trade remains fragile, there were some signs that declines in cargo demand were bottoming out.