Explosive screening begins at San Francisco, Seattle and Cincinnati airports

Testing of explosive scanning devices has begun at San Francisco, Seattle and Cincinnati airports to "establish a framework for how cargo screening will happen in the future," said a spokesman for the US Department of Homeland Security.

Each airport is focusing a difference aspect of the problem, reported The Cincinnati Inquirer.

San Francisco International Airport is testing extra technology, including X-rays and trace-explosives detectors. Seattle focuses on detecting stowaways using ultra-sensitive sound monitors, which can hear human heartbeats while Cincinnati/Northern Kentucky International Airport is using existing equipment to improve screening while making sure freight is moved in a timely fashion.