Malaysian Airline System Flight 653 (MH653) was a scheduled domestic flight from Penang to Kuala Lumpur in Malaysia, operated by Malaysian Airline System (MAS). On the evening of 4 December 1977, the Boeing 737-200 aircraft flying the service crashed at Tanjung Kupang, Johor, in Malaysia. It was the first—and is now the second-deadliest—fatal air crash for Malaysia Airlines (as MAS is now known); with all 93 passengers and 7 crew killed instantly. The flight was apparently hijacked as soon as it reached cruise altitude. The circumstances in which the hijacking and subsequent crash occurred remain unsolved.