What you are seeing here isn’t lightning, it’s static electricity on the window of a plane. It’s called Saint Elmo’s Fire. It occurs when the atmosphere becomes charged and an electrical potential strong enough to cause a discharge (plasma) is created between an object and the air around it. This can happen to an aircraft flying through heavily charged skies.
View from plane window showing storm clouds at night with flashing lights.
Lightning storm, non stop, barely audible thunder, for over an hour. I live about 60-70 miles from where most of the lightning was striking which was why it was inaudible.
Storm clouds seen from night flight above Munich. Very Cloudy and the City Lights shined through from below.