An iridium satellite, possibly some other type of satellite. Faint streak which flares as the panels reflect sunlight. I attached a picture of one I took.
The IIS tracker app tells you when the iridium flares are occurring. Happens just after dark and before dawn when the sun is just below the horizon, some brighter than others. Other types of satellite flare too, but the Iridium ones are most impressive.
More info:
https://en.wikipedia.org/wiki/Satellite_flare