Denver airport’s air traffic control was reportedly struck by a staggering six-minute outage earlier this week after several radio transmitters suddenly went dark. The frequency outage meant that as many as 20 pilots were unable to reach air traffic controllers as they descended into Denver International Airport on Monday afternoon, ABC7 reported, citing sources. A controller eventually made contact with one aircraft on a “guard line,” which is typically only used when a pilot is in distress. That pilot was then able to contact other nearby planes and tell them to switch radio frequencies, the sources said. At the time...