A quick science lesson for ya.
When you are talking about cloud to ground lightning (not cloud to cloud) there are two types.; natural, and artificial. Natural is caused from things that are part of the natural environment and the charges that cause the strike are natural, like when a tree is struck in a thunder storm. Artificial is when a man made item like a building or a plane is struck, and it is considered to be ‘’triggered’’ lightning. It’s not uncommon at all for planes to get hit by lightning. The bolt ‘s origin place is also different between the two types. In natural lightning the bolt started in the cloud and came down to strike the tree. In artificial or triggered lightning the bolt started from the object (in this case the plane) and went to the cloud AND to the ground. That was also a single bolt, not two. The reason lightning flashes is because the electricity is trying to equalize. It will bounce back and forth (or up and down) from the source to the cloud (or vice versa) multiple times in a split second until both charges are equal again. It happens so quickly that we refer to it as a flash. Just like when you toss a rock into a pond the waves dissipate outward until the energy is gone.