Only minutes into a doomed journey, the pilot of a business jet wasn’t responding to air traffic control instructions and federal aviation officials say the situation was soon reported to a network that includes military, security and law enforcement agencies. Despite being out of contact on its ascent Sunday, the jet that took off in Tennessee continued toward Long Island, then turned back toward Virginia, where it slammed into a mountain, killing four people. Family and friends identified two victims as an entrepreneur known in New York real-estate circles and her 2-year-old daughter. The ...