Malaysian Airline System Flight 653 (MH653/MAS653) 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, Malaysia, while purportedly being diverted by hijackers to Singapore. It was the first fatal air crash for Malaysia Airlines, with all 93 passengers and 7 crew killed. It is also the deadliest aviation disaster to occur on Malaysian soil. The flight was apparently hijacked as soon as it reached cruise altitude. The circumstances in which the hijacking and subsequent crash occurred remain unsolved.