This is the vapor trail of Aegean Airlines Flight A3840 from Athens to Dusseldorf as it flew over the South Tyrol. I took the photo from my office window at 11:40 am on Saturday and noted down that: “It is an Airbus A321-271NX aircraft, flying at 36,000 feet at a ground speed of 395 knots at the moment. Due to land in Dusseldorf at 12:03 pm (in 23 minutes), two minutes ahead of schedule.” Yes, you can pretty much instantly find out anything you want on the internet these days. Click it to see whole photo at once.