Traffic at the Des Moines airport continued to grow in April, according to monthly statistics released Monday by the airport. Passenger traffic was up 6.7 percent in April compared to the same month last year, and up 3.7 percent year-to-date. Cargo was up 15.9 percent in April compared to the same month last year, but is down about 1 percent year-to-date. Growth in Southwest Airline's traffic led that of other commercial carriers, growing almost 54 percent for the first four months of 2014 compared with the same period in 2013. US Airways also showed an increase of nearly 34 percent and Allegiant's traffic grew by nearly 8 percent over the same period. The other airlines showed less traffic with United Airlines dropping by the most - 12 percent. Chartered flights were down about 20 percent over the same period in 2013, according to the airport.