Boeing officials are drafting plans for all 747 operators to inspect the center fuel tanks of those aircraft for clues that might help investigators unmask the cause of Trans World Airlines Flight 800's destruction last summer.

The investigators for the National Transportation Safety Board have determined that Flight 800's center fuel tank exploded. While they have concluded that an explosive mixture of fuel and air probably was present in the nearly empty tank, and the explosion of that tank led to the aircraft's breakup, the investigators have so far been unable to identify what ignited those vapors.

In their search for the ignition source on Flight 800, NTSB investigators are assessing whether electrical bonding or grounding components on the aircraft somehow failed to prevent the buildup of a static charge in the tank. Those investigators have found no signs on the debris recovered from Flight 800's center tank of the arcing that might have resulted from the discharge of such a static buildup.

The NTSB is pushing the FAA, airlines and aircraft manufacturers to minimize the risks that a potential fuel-tank explosion poses to safe flight.