The Federal Bureau of Investigation briefly detained four AirTran Airways passengers Monday after two fellow passengers complained that one of them tore a Coke can, creating sharp metal edges, a spokesman for the airline said. The detained passengers, who included three men of Middle Eastern descent, were questioned and released after it was determined they were no threat. The incident involved AirTran Flight 273, after it arrived in Atlanta from Boston. Two business-class passengers became concerned when they saw one of the questioned men tear apart a Coke can and walk up and down the aisle talking to the others....