1.   At the time of the accident, Boeing was unsure whether explosive vapors could build up in the fuel tank.

2.   Also, Westinghouse has halted all drilling for core samples in the crusty residues of tanks with potentially explosive vapors.

3.   Extra fuel would keep the tank cooler, below the flash point of jet fuel, and cut the chance of fuel evaporating into explosive vapor.

4.   Investigators do not believe that pumps were running on that airplane, although the tank was nearly empty, which could allow an explosive vapor to develop.

5.   One area the panel will explore is whether it is possible to rid empty fuel tanks of explosive vapors.

6.   That approach is to eliminate all possible ignition sources and to reduce explosive vapors that build up in center fuel tanks.

7.   The board asked the Federal Aviation Administration in December to require that airline personnel adopt procedures that could help eliminate explosive vapors in the fuel tanks.

8.   The less fuel in the tank, the more potentially explosive vapors.

9.   The NTSB asked the FAA in December to require that airline personnel adopt procedures that could help eliminate explosive vapors in the fuel tanks.

10.   The safety board does know, however, that explosive vapors at extremely high temperatures existed in the near-empty center fuel tank.