KNKT.17.08.25.04 On 3 August 2017, a Boeing 737-900 landing at Medan was in collision in good daylight visibility with a departing ATR 72-500 also on the runway and both aircraft sustained substantial damage. Significant debris was deposited on the runway but there were no occupant injuries and both aircraft were taxied clear. Although ATC were advised of the debris, the runway was not closed until several minutes later after further use had occurred. The Investigation is continuing but has found that the ATR 72 failed to comply with its clearance and that an incomplete readback went unchallenged by ATC.