The Air Force stands ready to respond if hostilities between North Korea and South Korea escalate, the service's top uniformed officer said, but American fighter jets remained at their normal alert status a day after a North Korean artillery attack. The North fired artillery shells at the island of Yeonpyeong on Tuesday, killing two people and dramatically raising tensions between American-allied South Korea and the nuclear-armed north. Air Force Chief of Staff Gen. Norton Schwartz, in a meeting with reporters later that morning, said his service has plenty of firepower in the region and listed the bases from which the...