DENVER -- With three Secret Service agents aboard and the pilots fully in control of a United Airlines jetliner being diverted to Denver, two F-16 fighter jets scrambled to intercept the flight merely escorted the plane into Denver International Airport. But the apparatus that could ultimately have lead to the plane with 138 passengers and six crew members being shot down -- put in place after 911 -- was fully operational Friday, with agencies that included the Federal Aviation Administration and the Department of Homeland Security on an open phone line monitoring the flight. Had the plane "been judged as...