On 3 August 2017, a Boeing 737-900ER landing at Medan was in wing-to-wing collision as it touched down with an ATR 72-500 which had entered the same runway to depart at an intermediate point. Substantial damage was caused but both aircraft could be taxied clear. The Investigation concluded that the ATR 72 had entered the runway at an opposite direction without clearance after its incomplete readback had gone unchallenged by ATC. Controllers appeared not to have realized that a collision had occurred despite warnings of runway debris and the runway was not closed until other aircraft also reported debris.