31.   The safety board and the FBI are still searching for conclusive proof of the ignition source.

32.   The standards would require manufacturers to review the designs of their fuel-tank systems to insure that failures could not create ignition sources within the tanks.

33.   They drew up a list of five possible ignition sources.

34.   They never did find the ignition source for the explosion.

35.   Vapors from a leak or rupture could speed along at ground level until an ignition source is reached.

36.   If the gas is concentrated and finds an ignition source, it could cause an explosion and fire.

37.   If an ignition source had been present, the flammable gases could have exploded.

38.   That could lead to fuel leakage, which could cause a fire in the presence of an ignition source.

39.   The FAA has insisted that the problem can be resolved by eliminating any ignition source near the tank.

40.   The FAA has instead looked at eliminating ignition sources around the tank.