Hillary Clinton was aboard an American Airlines flight from New York that suffered a mechanical issue and needed to return to the gate Sunday afternoon, according to a law enforcement source. A separate law enforcement source confirmed Clinton was aboard a plane which experienced a mechanical issue that needed to return to the gate. American Airlines says flight 2144, from New York's LaGuardia Airport to Washington's Reagan National Airport returned to the gate around 3:15 pm, ET, after ground personnel saw the mechanical issue, according to the source. Pilots told authorities the plane shook and ground personnel saw smoke and...