1.   A discharge of static electricity near the filler pipe could ignite gasoline vapors.

2.   It does not migrate into the interior of the aircraft, where it might threaten to ignite fuel vapors, according to several aviation engineers.

3.   NTSB investigators concluded that the plane was blown apart when volatile fuel vapors in the empty center tank were ignited.

4.   The board said a spark of unknown origin in the tank apparently ignited the vapors.

5.   The flame arrestor would help prevent an outside spark or flame from igniting fuel vapors in the tank.

6.   There are several conceivable sources of a possible spark that could have ignited the vapors.

7.   But coast guard officials who boarded the vessel to inspect it Wednesday said there was a danger of sparks igniting the vapors.

8.   Federal safety investigators believe that a spark in the wiring ignited vapors in a fuel tank.

9.   Manufacturers were told to design new planes to reduce the chances of igniting fuel vapors in the tanks.

10.   Manufacturers were told to design new planes to reduce chances of igniting fuel vapors in the tanks.