On 16 November 2012, Captain of an A320 positioning for approach to Abu Dhabi at night became incapacitated due to a stroke. The First Officer took over control and declared a MAYDAY to ATC. The subsequent approach and landing were uneventful but since the First Officer was not authorised to taxi the aircraft, it was towed to the gate for passenger disembarkation. The investigation found that the Captain had an undiagnosed medical condition which predisposed him towards the formation of blood clots in arteries and veins.