1.   A static spark too weak to see in daylight can be strong enough to ignite a mixture of fuel vapor and air in the ideal concentrations.

2.   Even so, the attraction of a static spark as a theory is clear.

3.   If the tank had been full of cold fuel, or nearly so, a static spark probably would not have ignited it.

4.   Investigators have seized on the idea of a static spark or a tiny explosive device, neither of which would necessarily have left enough evidence to be detected.

5.   Like the tiny, undetectable explosive device, a static spark is a theoretical possibility.

6.   Proving that a static spark is possible, though, does not prove that it happened.

7.   The aviation investigators have settled on a static spark as a likely culprit because all other identified mechanical ignition sources appear even less likely.

8.   The report said a static spark caused the explosion of a fuel tank when it came into contact with an air-fuel mixture.