Trans World Airlines Flight 840 was a regularly scheduled flight from Los Angeles to Cairo via New York City, Rome, and Athens on April 2, 1986. About 20 minutes before landing in Athens, a bomb was detonated on the aircraft while it was over Argos, Greece, blasting a hole in the plane's starboard side. Four passengers died after being blown out, while another seven were injured by flying shrapnel and debris. The aircraft then made a successful emergency landing with no further loss of life.^[4]

The Boeing 727-231 involved in the incident was delivered to TWA in 1974, with the registration N54340.^[5][6] It was fitted with 3 P&W JT8D-5 turbofan engines.^[5]

The flight originated in Los Angeles on a Boeing 747 and transferred to a Boeing 727 in Rome for the remainder of the flight.^[7] After taking off from Rome, Italy, the flight remained uneventful until around 20 minutes before landing at Athens, when the aircraft was at around 11,000 feet (3,400 m).^[8] A bomb hidden underneath seat 10F during an earlier leg of the flight detonated, blasting a hole in the starboard side of the fuselage in front of the wing.^[7]

Four American passengers, including an eight-month-old infant, were ejected through the hole to their deaths below. The victims were identified as a Colombian-American man; and a woman, her daughter, and her infant granddaughter.^[7] Seven others on the aircraft were injured by shrapnel as the cabin suffered a rapid decompression. However, as the aircraft was in the middle of its approach to Athens, the explosion wasn't as catastrophic as it would have been at a higher altitude.^[7] The remaining 110 passengers survived the incident as pilot Richard "Pete" Petersen made an emergency landing.^[7]

The bodies of three of the four victims were later recovered from an unused Greek Air Force landing strip near Argos; the fourth was found in the sea.^[7]

A group calling itself the Arab Revolutionary Cells claimed responsibility, saying it was committed in retaliation for American imperialism and clashes with Libya in the Gulf of Sidra the week before.^[9]

The aircraft was substantially damaged but was repaired and returned to service until TWA ceased operations in 2001. The aircraft was scrapped in 2002.^[10]

Investigators concluded that the bomb contained one pound of plastic explosive. As the bomb was placed on by the floor of the cabin, the explosion tore a hole downward, where the fuselage absorbed the most damage. It is suspected it had been placed beneath the seat on a previous journey by a Lebanese woman (later arrested, never convicted) who worked for the Abu Nidal Organisation, which was dedicated to the destruction of the state of Israel.^[11] They had previously hijacked and bombed several other aircraft, as well as committing various terrorist attacks in parts of the Middle East.^[12]

• Daallo Airlines Flight 159 - Similar incident in which a suicide bomber detonated a bomb on board, whereafter the plane managed to make a successful emergency landing
• Philippine Airlines Flight 434 - A 747 where a bomb went off, followed by a successful emergency landing
• Pan Am Flight 830 - Another 747 that landed safely after a bomb exploded
• United Airlines Flight 811 - Experienced an explosion after the cargo door opened in mid-flight, causing several passengers to be blown out of the aircraft
• List of accidents and incidents involving commercial aircraft