NATO has raised the security level at its air base in the western German town of Geilenkirchen to the second-highest level, Charlie, following intelligence reports of a potential threat. As a precautionary measure, all employees who are not needed for the operation have been sent home, a spokesman for the air base said late on Thursday. He said the decision was based on intelligence information indicating a potential threat. In NATO terms, security level Charlie means that there has been an incident or that there is evidence suggesting a high likelihood of terrorist action against the alliance…