In January 1984, ball of lightning measuring about four inches in diameter entered a Russian passenger aircraft and, according to the Russian news release, "flew above the heads of the stunned passengers. In the tail section of the airliner, it divided into two glowing crescents which then joined together again and left the plane almost noiselessly." The ball of lightning left two holes in the plane.
Ball of lightning is another natural phenomena for which science has yet to come up with a full explanation.
The problem for scientists is that the manifestation of the phenomenon is so rare that it is almost impossible to study. Attempts have been made to recreate it artificially in the laboratory, but an actual specimen of naturally occurring ball of lightning has yet to be captured for study. This may be impossible since the phenomenon is fleeting - floating about for awhile and then fading away or exploding with a loud pop.
What makes ball of lighting so fascinating and puzzling is its strange "behavior." Witnesses have said that it moves about as if with a kind of intelligence, following patterns on walls or furniture, and seeming to avoid obstacles. More mysterious still is its ability to pass through solid objects. Sometimes it leaves holes, as with the airliner above, but it has also been seen to pass through window glass and even walls without even leaving a mark.