A disaster was averted when a Jet Airways flight with 140 passengers on board aborted take-off after a private helicopter entered the runway at the Sahara Airport on Wednesday afternoon.In the second incident of its kind in 15 days, Jet flight 9W-417 bound for Bangalore had almost started its takeoff run when the pilot saw the Bell-430 helicopter operated by the Essar Group enter the runway. An inquiry has been ordered into the incident by the office of the Directorate General of Civil Aviation here.The Air Traffic Control had cleared both aircrafts for takeoff but the helicopter was asked by the authority to hold at the taxiway. ‘‘However, the helicopter pilot just took off,’’ an airport source said. ‘‘Seeing the helicopter in front of him, the surprised Jet pilot aborted take-off.’’The source said an accent problem might be the cause: the foreign pilot may have misunderstood ATC instructions. ‘‘We are trying to find out who was at fault,’’ said GM (Aerodrome) Pravin Ohri.In the incident on February 1, the ATC managed to pull back a private aircraft that entered the main runway even as a Jet flight from Bangalore was cleared for landing.