(Kazakhstan Airlines flight 1907 is approaching New Dehi ,from Air Crash Investigation)

Kazakhstan Airlines Flight 1907, an Ilyushin Il-76 departed Shymkent (aka Chimkent), Kazakhastan for a flight to Delhi. While descending on Airway G452 the crew contacted Delhi: "Good evening 1907. Passing through 230 for 180, 74 miles from DPN [the Delhi Airport beacon]". The controller then cleared the flight to descend to and report at FL150. In the meantime, a Saudi Arabian Airlines Boeing 747 had departed Delhi at 18:32 for a passenger flight to Dhahran. Flight SV763 followed the Parvi SID and reported approaching FL100. The Delhi controller cleared the flight, which was also on Airway G452, to climb to FL140. Because Flight 1907 was approaching from the opposite side, the controller told SV763: "Maintain level 140, Standby for higher." A little later, Flight 1907 reported reaching FL150 at 46 miles from the airport. The controller then responded: "Roger. Maintain 150. Identified traffic 12 o'clock, reciprocal Saudia Boeing 747, 14 miles. Report in sight." The Kazakhstan crew replied by querying the distance to which the controller answered: "Fourteen miles now, roger 1907." When no reply followed he again warned: "Traffic in 13 miles, level 140."Apparently the Kazakh aircraft had descended below its assigned altitude and was flying at 14500 feet. A few seconds later seconds later the Ilyushin had descended another 310 feet. Shortly afterwards both aircraft collided, plummeted down in flames and crashed in an arid farming area.

Probable Cause: The root and approximate cause of the collision was the unauthorised descending by the Kazak aircraft to FL-140 and failure to maintain the assigned FL-150.The factors contributing to the unauthorised descent of Kazak aircraft to FL-140, departing from the assigned FL-150, were:i) inadequate knowledge of English language of Kazak pilot, resulting in wrong interpretations of ATC instructions.ii) poor airmanship and lack of proper CRM (Crew Resource Management) skill on the part of PIC (Pilot-in-Command) compo