TWA Flight 800 Part I

Trans World Airlines Flight 800 (TWA800) was a Boeing 747-100 that exploded and crashed into the Atlantic Ocean near East Moriches, New York, on July 17, 1996, at about 8:31 pm. EDT, 12 minutes after takeoff from John F. Kennedy International Airport, on a scheduled international passenger flight to Rome, with a stopover in Paris. All 230 people on board died in the crash; it is the third-deadliest aviation accident in U.S. history. Accident investigators from the National Transportation Safety Board (NTSB) traveled to the scene, arriving the following morning amid speculation that a terrorist attack was the cause of the crash. Consequently, the Federal Bureau of Investigation (FBI) and New York Police Department Joint Terrorism Task Force (JTTF) initiated a parallel criminal investigation. Sixteen months later, the JTTF announced that no evidence of a criminal act had been found and closed its active investigation.

The four-year NTSB investigation concluded with the approval of the Aircraft Accident Report on August 23, 2000, ending the most extensive, complex and costly air disaster investigation in U.S. history at that time. The report's conclusion was that the probable cause of the accident was explosion of flammable fuel vapors in the center fuel tank. Although it could not be determined with certainty, the likely ignition source was a short circuit.  Problems with the aircraft's wiring were found, including evidence of arcing in the fuel quantity indication system (FQIS) wiring that enters the tank. The FQIS on Flight 800 is known to have been malfunctioning; the captain remarked on "crazy" readings from the system about 2 minutes and 30 seconds before the aircraft exploded. As a result of the investigation, new requirements were developed for aircraft to prevent future fuel tank explosions.

Accident flight

The accident airplane, registration N93119 (a Boeing 747-131), was manufactured by Boeing in July 1971; it had been ordered by Eastern Air Lines, but after Eastern cancelled its 747 orders, the plane was purchased new by Trans World Airlines. The aircraft had completed 16,869 flights with 93,303 hours of operation and was powered by four Pratt & Whitney JT9D-7AH turbofan engines. On the day of the accident, the airplane departed from Ellinikon International Airport in Athens, Greece, as TWA Flight 881 and arrived at John F. Kennedy International Airport (JFK) about 4:38 pm. The aircraft was refueled, and a crew change was made; the new flight crew consisted of 58-year-old Captain Ralph G. Kevorkian (who had flown for TWA for 31 years and the U.S. Air Force for 9 years), 57-year-old Captain/Check Airman Steven E. Snyder (who had flown for TWA for 32 years), and 63-year-old Flight Engineer/Check Airman Richard G. Campbell Jr. (who had flown for TWA for 30 years and the U.S. Air Force for 12 years), as well as 25-year-old flight engineer trainee Oliver Krick (who previously served as a business pilot for 4 years), who had flown for TWA for 26 days and was starting the sixth leg of his initial operating experience training.

The ground-maintenance crew locked out the thrust reverser for engine #3 (treated as a minimum equipment list item) because of technical problems with the thrust reverser sensors during the landing of TWA 881 at JFK, prior to Flight 800's departure. Additionally, severed cables for the engine #3 thrust reverser were replaced. During refueling of the aircraft, the volumetric shutoff (VSO) control was believed to have been triggered before the tanks were full. To continue the pressure fueling, a TWA mechanic overrode the automatic VSO by pulling the volumetric fuse and an overflow circuit breaker. Maintenance records indicate that the aircraft had numerous VSO-related maintenance writeups in the weeks before the accident.

TWA 800 was scheduled to depart JFK for Charles de Gaulle Airport around 7:00 pm, but the flight was delayed until 8:02 pm by a disabled piece of ground equipment and a passenger/baggage mismatch.  After the owner of the baggage in question was confirmed to be on board, the flight crew prepared for departure, and the aircraft pushed back from Gate 27 at the TWA Flight Center. The flight crew started the engines at 8:04 pm. However, because of the previous maintenance undertaken on engine #3, the flight crew only started engines #1, #2, and #4. Engine #3 was started 10 minutes later at 8:14 pm. Taxi and takeoff proceeded uneventfully.

TWA 800 then received a series of heading changes and generally increasing altitude assignments as it climbed to its intended cruising altitude.  Weather in the area was light winds with scattered clouds,  with dusk lighting conditions.  The last radio transmission from the airplane occurred at 8:30 pm, when the flight crew received and then acknowledged instructions from Boston Center to climb to 15,000 feet (4,600 m). The last recorded radar transponder return from the airplane was recorded by the Federal Aviation Administration (FAA) radar site at Trevose, Pennsylvania, at 8:31:12 pm. 

Thirty-eight seconds later, the captain of an Eastwind Airlines Boeing 737 reported to Boston ARTCC that he "just saw an explosion out here", adding, "we just saw an explosion up ahead of us here ... about 16,000 feet [4,900 m] or something like that, it just went down into the water." Subsequently, many air traffic control facilities in the New York/Long Island area received reports of an explosion from other pilots operating in the area. Many witnesses in the vicinity of the crash stated that they saw or heard explosions, accompanied by a large fireball or fireballs over the ocean, and observed debris, some of which was burning while falling into the water.  Various civilian, military, and police vessels reached the crash site and searched for survivors within minutes of the initial water impact, but found none,  making TWA 800 the second-deadliest aircraft accident in United States history at that time.

Passengers and crew

On board TWA 800 were 230 people, including 18 crew and 20 off-duty employees, most of whom were crew meant to cover the Paris-Rome leg of the flight. Seventeen of the 18 crew members and 152 of the passengers were Americans; the remaining crew member was Italian, while the remaining passengers were of various other nationalities. Notable passengers included:

Michel Breistroff, French ice hockey player

Marcel Dadi, French guitarist

Lawrence Harris, American fashion photographer

David Hogan, American composer

Jed Johnson, Andy Warhol's partner of twelve years, interior designer, and director

Pam Lychner, American crime victims' rights advocate and former TWA flight attendant

Rico Puhlmann, German fashion photographer

Courtney Elizabeth Johns, Sister of Geoff Johns and was the inspiration for Courtney Whitemore

Ana Marie Shorter, Wayne Shorter's second wife

In addition, 16 students and five adult chaperones from the French Club of the Montoursville Area High School in Pennsylvania were on board.

Initial investigation

The NTSB was notified about 8:50 pm the day of the accident; a full "go team" was assembled in Washington, DC, and arrived on scene early the next morning.  Meanwhile, initial witness descriptions led many to believe the cause of the crash was a bomb or surface-to-air missile attack. Since the NTSB does not investigate criminal activity, the United States Attorney General is empowered to declare an investigation to be linked to a criminal act, and require the NTSB to relinquish control of the investigation to the FBI. In the case of TWA 800, the FBI initiated a parallel criminal investigation alongside the NTSB's accident investigation.

Search and recovery operations

Search and recovery operations were conducted by federal, state, and local agencies, as well as government contractors.  An HH-60 Pave Hawk helicopter of the New York Air National Guard saw the explosion from about 8 miles away; it arrived at the scene of the explosion while debris was still in the process of falling into the water, forcing the crew to pull away. They reported their sighting to the tower at Suffolk County Airport. Remotely operated vehicles (ROVs), side-scan sonar, and laser line-scanning equipment were used to search for and investigate underwater debris fields. Victims and wreckage were recovered by scuba divers and ROVs; later scallop trawlers were used to recover wreckage embedded in the sea floor. In one of the largest diver-assisted salvage operations ever conducted, often working in very difficult and dangerous conditions, over 95% of the airplane wreckage was eventually recovered.  The search and recovery effort identified three main areas of wreckage underwater;  the yellow zone, red zone, and green zone contained wreckage from front, center, and rear sections of the airplane, respectively.  The green zone with the aft portion of the aircraft was located the furthest along the flight path.

Pieces of wreckage were transported by boat to shore and then by truck to leased hangar space at the former Grumman Aircraft facility in Calverton, New York, for storage, examination, and reconstruction.  This facility became the command center and headquarters for the investigation.  NTSB and FBI personnel were present to observe all transfers to preserve the evidentiary value of the wreckage. The cockpit voice recorder and flight data recorder were recovered by U.S. Navy divers one week after the accident; they were immediately shipped to the NTSB laboratory in Washington, DC, for readout. The victims' remains were transported to the Suffolk County Medical Examiner's Office in Hauppauge, New York.

Tensions in the investigation

Relatives of TWA 800 passengers and crew, as well as the media, gathered at the Ramada Plaza JFK Hotel. Many waited until the remains of their family members had been recovered, identified, and released. This hotel became known as the "Heartbreak Hotel" for its role in handling families of victims of several airliner crashes.

Grief turned to anger at TWA's delay in confirming the passenger list, conflicting information from agencies and officials,  and mistrust of the recovery operation's priorities. Although NTSB Vice Chairman Robert Francis stated that all bodies were being retrieved as soon as they were spotted, and that wreckage was being recovered only if divers believed that victims were hidden underneath, many families were suspicious that investigators were not being truthful, or withholding information.

Much anger and political pressure was also directed at Suffolk County Medical Examiner Dr. Charles V. Wetli, as recovered bodies backlogged at the morgue. Under constant and considerable pressure to identify victims with minimal delay, pathologists worked nonstop. While some victims' bodies were mostly intact, most were either burned, fragmented, skeletonized, or decaying, so they had to be identified by DNA testing and dental records.  Since the primary objective was to identify all remains rather than performing a detailed forensic autopsy, the thoroughness of the examinations was highly variable. Ultimately, remains of all 230 victims were recovered and identified, the last over 10 months after the crash.

With lines of authority unclear, differences in agendas and culture between the FBI and NTSB resulted in discord.  The FBI, from the start assuming that a criminal act had occurred, saw the NTSB as indecisive. Expressing frustration at the NTSB's unwillingness to speculate on a cause, one FBI agent described the NTSB as "No opinions. No nothing." Meanwhile, the NTSB was required to refute or play down speculation about conclusions and evidence, frequently supplied to reporters by law enforcement officials and politicians.  The International Association of Machinists and Aerospace Workers, an invited party to the NTSB investigation, criticized the undocumented removal by FBI agents of wreckage from the hangar where it was stored.

Witness interviews

Although considerable discrepancies existed between different accounts, most witnesses to the accident had seen a "streak of light" that was described by 38 of 258 witnesses as ascending,  moving to a point where a large fireball appeared, with several witnesses reporting that the fireball split in two as it descended toward the water.  Intense public interest arose in these witness reports, as did much speculation that the reported streak of light was a missile that had struck TWA 800, causing the airplane to explode. These witness accounts were a major reason for the initiation and duration of the FBI's criminal investigation.

Around 80 FBI agents conducted interviews with potential witnesses daily. No verbatim records of the witness interviews were produced; instead, the agents who conducted the interviews wrote summaries that they then submitted.  Witnesses were not asked to review or correct the summaries.  Included in some of the witness summaries were drawings or diagrams of what the witness observed.

Within days of the crash, the NTSB announced its intent to form its own witness group and to interview witnesses to the crash. After the FBI raised concerns about nongovernmental parties in the NTSB's investigation having access to this information and possible prosecutorial difficulties resulting from multiple interviews of the same witness, the NTSB deferred and did not interview witnesses to the crash. A safety board investigator later reviewed FBI interview notes and briefed other board investigators on their contents. In November 1996, the FBI agreed to allow the NTSB access to summaries of witness accounts in which personally identifying information had been redacted and to conduct a limited number of witness interviews. In April 1998, the FBI provided the NTSB with the identities of the witnesses, but due to the time elapsed, a decision was made to rely on the original FBI documents rather than reinterview witnesses.

Further investigation and analysis

Examination of the cockpit voice recorder (CVR) and flight data recorder data showed a normal takeoff and climb,  with the aircraft in normal flight before both abruptly stopped at 8:31:12 pm. At 8:29:15 pm, Captain Kevorkian was heard to say, "Look at that crazy fuel flow indicator there on number four... see that?" A loud noise recorded on the last few tenths of a second of the CVR was similar to the last noises recorded from other airplanes that had experienced in-flight breakups. This, together with the distribution of wreckage and witness reports, all indicated a sudden catastrophic in-flight breakup of TWA 800.

Possible causes of the in-flight breakup

Investigators considered several possible causes for the structural breakup - structural failure and decompression, detonation of a high-energy explosive device, such as a missile warhead exploding either upon impact with the airplane, or just before impact, a bomb exploding inside the airplane, or a fuel-air explosion in the center wing fuel tank.

Structural failure and decompression

Close examination of the wreckage revealed no evidence of structural faults such as fatigue, corrosion, or mechanical damage that could have caused the in-flight breakup.  The breakup also could have been initiated by an in-flight separation of the forward cargo door like the disasters on board Turkish Airlines Flight 981 or United Airlines Flight 811, but all evidence indicated that the door was closed and locked at impact. The NTSB concluded that "the in-flight breakup of TWA flight 800 was not initiated by a pre-existing condition resulting in a structural failure and decompression."

Missile or bomb detonation

A review of recorded data from long-range and airport surveillance radars revealed multiple contacts of airplanes or objects in TWA 800's vicinity at the time of the accident. None of these contacts intersected TWA 800's position at any time.  Attention was drawn to data from the Islip, New York, ARTCC facility that showed three tracks in the vicinity of TWA 800 that did not appear in any of the other radar data.  None of these sequences intersected TWA 800's position at any time, either.  All the reviewed radar data showed no radar returns consistent with a missile or other projectile traveling toward TWA 800.

The NTSB addressed allegations that the Islip radar data showed groups of military surface targets converging in a suspicious manner in an area around the accident, and that a 30-knot radar track, never identified and 3 nautical miles (5.6 km; 3.5 mi) from the crash site, was involved in foul play, as evidenced by its failure to divert from its course and assist with the search and rescue operations. Military records examined by the NTSB showed no military surface vessels within 15 nautical miles (28 km; 17 mi) of TWA 800 at the time of the accident. In addition, the records indicated that the closest area scheduled for military use, warning area W-387A/B, was 160 nautical miles (296 km; 184 mi) south.

The NTSB reviewed the 30-knot target track to try to determine why it did not divert from its course and proceed to the area where the TWA 800 wreckage had fallen. TWA 800 was behind the target, and with the likely forward-looking perspective of the target's occupant(s), the occupants would not have been in a position to observe the aircraft's breakup or subsequent explosions or fireball(s). Additionally, the occupants of the target track were unlikely to have been able to hear the explosions over the sound of its engines and the noise of the hull traveling through water, even more so if the occupants were in an enclosed bridge or cabin.  Further, review of the Islip radar data for other similar summer days and nights in 1999 indicated that the 30-knot track was consistent with normal commercial fishing, recreational, and cargo vessel traffic.

Trace amounts of explosive residue were detected on three samples of material from three separate locations of the recovered airplane wreckage (described by the FBI as a piece of canvas-like material and two pieces of a floor panel).  These samples were submitted to the FBI's laboratory in Washington, DC, which determined that one sample contained traces of cyclotrimethylenetrinitramine (RDX), another nitroglycerin, and the third a combination of RDX and pentaerythritol tetranitrate (PETN);  these findings received much media attention at the time. In addition, the backs of several damaged passenger seats were observed to have an unknown red/brown-shaded substance on them. According to the seat manufacturer, the locations and appearance of this substance were consistent with adhesive used in the construction of the seats, and additional laboratory testing by NASA identified the substance as being consistent with adhesives.

Further examination of the airplane structure, seats, and other interior components found no damage typically associated with a high-energy explosion of a bomb or missile warhead ("severe pitting, cratering, petalling, or hot-gas washing"). This included the pieces on which trace amounts of explosives were found. Of the 5% of the fuselage that was not recovered, none of the missing areas was large enough to have covered all the damage that would have been caused by the detonation of a bomb or missile.  None of the victims' remains showed any evidence of injuries that could have been caused by high-energy explosives.

The NTSB considered the possibility that the explosive residue was due to contamination from the aircraft's use in 1991 transporting troops during the Gulf War or its use in a dog-training explosive detection exercise about one month before the accident. Testing conducted by the FAA's Technical Center indicated that residues of the type of explosives found on the wreckage would dissipate completely after two days of immersion in sea water (almost all recovered wreckage was immersed longer than two days).  The NTSB concluded that it was "quite possible" that the explosive residue detected was transferred from military ships or ground vehicles, or the clothing and boots of military personnel, onto the wreckage during or after the recovery operation and was not present when the aircraft crashed into the water.

Although it was unable to determine the exact source of the trace amounts of explosive residue found on the wreckage, the lack of any other corroborating evidence associated with a high-energy explosion led the NTSB to conclude, "the in-flight breakup of TWA flight 800 was not initiated by a bomb or missile strike."

Fuel-air explosion in the center wing fuel tank

To evaluate the sequence of structural breakup of the airplane, the NTSB formed the Sequencing Group, which examined individual pieces of the recovered structure, two-dimensional reconstructions or layouts of sections of the airplane, and various-sized three-dimensional reconstructions of portions of the airplane.  In addition, the locations of pieces of wreckage at the time of recovery and differences in fire effects on pieces that are normally adjacent to each other were evaluated.  The Sequencing Group concluded that the first event in the breakup sequence was a fracture in the wing center section of the aircraft, caused by an "over-pressure event" in the center wing fuel tank (CWT).  An over-pressure event was defined as a rapid increase in pressure resulting in failure of the structure of the CWT. 

Because no evidence was found that an explosive device detonated in this (or any other) area of the airplane, this over-pressure event could only have been caused by a fuel-air explosion in the CWT.  There were 50 US gal (190 L) of fuel in the CWT of TWA 800; tests recreating the conditions of the flight showed the combination of liquid fuel and fuel-air vapor to be flammable. A major reason for the flammability of the fuel-air vapor in the CWT of the 747 was the large amount of heat generated and transferred to the CWT by air conditioning packs located directly below the tank;  with the CWT temperature raised to a sufficient level, a single ignition source could cause an explosion.

Computer modeling  and scale-model testing  were used to predict and demonstrate how an explosion would progress in a 747 CWT. During this time, quenching was identified as an issue, where the explosion would extinguish itself as it passed through the complex structure of the CWT. Because the research data regarding quenching were limited, a complete understanding of quenching behavior was not possible, and the issue of quenching remained unresolved.

To better determine whether a fuel-air vapor explosion in the CWT would generate sufficient pressure to break apart the fuel tank and lead to the destruction of the airplane, tests were conducted in July and August 1997, using a retired Air France 747 at Bruntingthorpe Airfield, England. These tests simulated a fuel-air explosion in the CWT by igniting a propane-air mixture; this resulted in the failure of the tank structure due to over-pressure.  While the NTSB acknowledged that the test conditions at Bruntingthorpe were not fully comparable to the conditions that existed on TWA 800 at the time of the accident,  previous fuel explosions in the CWTs of commercial airliners such as Avianca Flight 203 and Philippine Airlines Flight 143 confirmed that a CWT explosion could break apart the fuel tank and lead to the destruction of an airplane.

Ultimately, based on "the accident airplane's breakup sequence; wreckage damage characteristics; scientific tests and research on fuels, fuel tank explosions, and the conditions in the CWT at the time of the accident; and analysis of witness information,"  the NTSB concluded that "the TWA flight 800 in-flight breakup was initiated by a fuel/air explosion in the CWT."

In-flight breakup sequence and crippled flight

Fire damage and soot deposits on the recovered wreckage indicated that some areas of fire existed on the airplane as it continued in crippled flight after the loss of the forward fuselage.  After about 34 seconds (based on information from witness documents), the outer portions of both the right and left wings failed.  Shortly after, the left wing separated from what remained of the main fuselage, which resulted in further development of the fuel-fed fireballs as the pieces of wreckage fell to the ocean.

Only the FAA radar facility in North Truro, Massachusetts, using specialized processing software from the United States Air Force 84th Radar Evaluation Squadron, was capable of estimating the altitude of TWA 800 after it lost power due to the CWT explosion. Because of accuracy limitations, these radar data could not be used to determine whether the aircraft climbed after the nose separated. Instead, the NTSB conducted a series of computer simulations to examine the flight-path of the main portion of the fuselage.  Hundreds of simulations were run using various combinations of possible times the nose of TWA 800 separated (the exact time was unknown), different models of the behavior of the crippled aircraft (the aerodynamic properties of the aircraft without its nose could only be estimated), and longitudinal radar data (the recorded radar tracks of the east/west position of TWA 800 from various sites differed). These simulations indicated that after the loss of the forward fuselage the remainder of the aircraft continued in crippled flight, then pitched up while rolling to the left (north),  climbing to a maximum altitude between 15,537 and 16,678 feet (4,736 and 5,083 m) from its last recorded altitude, 13,760 feet (4,190 m).