In the night of the 20th to the 21st of May in 2019 Alfouine and I were able to observe the ISS on the same orbit.
At site 1 (Tours in Loire Valley, France) the ISS reached the highest altitude of 72° at 22:49:27 CET.
The ISS took 2 minutes and 42 seconds, covering 1,485 km to get to Vienna, Austria.
Here, at site 2, the ISS was perfectly visible. The sky had only some clouds close to the horizon, but from the point at which I first discovered the ISS I was able to see it until it came close to the horizon again and was getting smaller and smaller.
The ISS came into sight in the west at around 22:49 CET and had its highest altitude at 61° at 22:52:09 CET in NNW direction. At the end of it's travel across our sky it slowly vanished at the horizon in ENE direction at 22:56 CET.
I was surprised to see that the ISS was significantly brighter than the stars around it and that it was clearly visible although there was much light from the city around me.
Thanks to Alfouine for thinking about me being his partner and for all the help he provided.