Was there a problem with the plane?

The FBI's decision to suspend its investigation into a possible criminal explanation for the crash left investigators with only one scenario: that the plane was downed by some type of mechanical failure.

Tests conducted by Boeing after the crash showed that temperatures in the nearly empty center tank of TWA 800 were high enough to have caused the mixture of fuel vapor and air to ignite.

Investigators have theorized that those vapors could have been heated to the point of ignition by air conditioner units while the plane sat on the runway before takeoff. Alternatively, they've considered the possibility that that sparks caused by faulty wiring or static electricity may have ignited the vapors.

While the National Transportation Safety Board has reached no definite conclusions, as a precaution, it has urged the Federal Aviation Administration to consider forcing airlines to pump inert gases into fuel tanks to prevent explosions.

As an more immediate preventive step, the NTSB has asked the FAA to require airlines to refuel from ground tanks, which keep fuel cooler, and to carry an "appropriate" minimum amount of fuel in the tanks, since tanks are more prone to ignition when nearly empty than when they are full. [NTSB Safety Recommendation, December 13, 1996]

Boeing has also asked airlines flying the 747 to inspect the electrical insulation of fuel pump wires. As of June 6, 203 airplanes had been inspected, and about 7 percent needed servicing.

While fuel tank fires or explosions are extremely rare, they do happen. In a December 1996 report, the NTSB identified two accidents to illustrate its safety concerns about explosive vapors in fuel tanks.

• Bomb Theory
• Missile Theory
• Crash Theory Main Page