X marks the spot!

For the past couple of days I’ve noticed contrails (condensation trails that airplanes make when flying in the colder air above) that looked like “clouds” that created a giant X in the sky overhead (Vienna). I’ve taken a picture with my cell phone of the ones I saw yesterday around the same time as today around 10:00 am. The reason I mention this is because I really wonder what they are because they hang around for at least a couple of hours and travel as an X through the sky?  X marks the spot? I watched the sky yesterday and today, as I have done in the past when I saw these things. I tried to see other airplanes flying that made these same contrails to compare them and see how cold it is up there but the contrails of these airplanes I see dissipate almost right away or a few minutes later. Another thing is  that these contrails don’t match the flight patterns of the airplanes when they fly overhead. I’ve taken quite a few pictures of these “contrails” and being a hobby meteorologist, I am puzzled as to what these things are.  They don’t fit the wind patterns or cloud patterns whenever they appear. So, what are they? Chemtrails?