After two years of either flat or slightly negative traffic growth, demand for air cargo transport began to grow slowly and steadily during the second quarter of 2013. The uptick in traffic continued into the second half of 2013 to end the year 0.9 percent above the 2012 traffic total. Growth has continued to gather strength in 2014, nearly recovering the long-term trend rate. World air cargo traffic is forecast to grow an average 4.7 percent per year over the next 20 years to reach a total of more than twice the number of revenue tonne-kilometers (RTK) logged in 2013. The number of airplanes in the freighter fleet will increase by more than half by the end of the forecast period.