Southwest Airlines has started an international airfreight service, initially servicing Mexico City but shortly due to expand to three further cities. That follows an 8% rate of growth in overall airfreight handling by North American airlines globally in the 12 months to May 31. The growth in traffic between Mexico and the U.S. has been significantly quicker than that with freight worth $13 billion being carried in the 12 months to June 30 after a 22% increase on a year earlier. Shipments from Mexico City grew even faster at 38% over the same period. Continued growth will depend on NAFTA...