Flying object outside of aircraft.On WestJet flight 166 from YVR to YEG, we spotted an object out our starboard window, approximately 700-1000 meters from the plane.It was about 40-50 minutes into our flight. We had reached cruising altitude approx. 35k ft.When we first saw it, it looked like a large ball at the front with a long net-like or skirt-like structure trailing it. At first we thought it was a scratch on the window, then it started moving in a flowing like manner.The ball shape at the front was always at the lead of the direction it was moving. Same direction as the plane - or so it appeared.It was black.We were stunned and trying to understand what we were looking at for about 1-2 minutes before I started taking pictures. At that point it had flattened out or turned and appeared flat.The object was by our side for approximately 3 minutes until we past it.It had structure. It was not smoke or a contrail.I can only roughly approximate the size as it was far away but close enough to see detail. 10-15 meters long and 5 meters wide when spread out.We stayed on the plane until everyone had left and asked the pilots if they saw it. They said they did not.Trying to understand what it was. Can't explain it currently. Looking for help or someone that has seen something similar.It was a safety concern. It was close to the plane. Whatever it was, if it got in the engines, it would have been trouble.Thought it might be a drone, but that is high for a drone, especially with the long thing flying behind it.Aerodynamically, the flowing skirt doesn't make sense. It creates drag. Kites use ribbons for stabilizers, not for lift. Only thing similar I can think of is a sail, but the ball thing was at the lead, not the skirt.Photos and video:https://www.dropbox.com/sh/zrq9uorr1vbsm46/AACbF_Xk5wWWLRVZ90o1GPSHa?dl=0 The video is faint. You see it similar to the photos when zoomed in on the video on my iPhone. Don't know if you have a way to zoom into the video.A sketch is included, but we need more detail. I'm attempting to sketch it further.((NUFORC Note: We spoke via telephone with the witness, and we found him to be quite sober minded. We have requested that the other witness submit

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• https://www.dropbox.com/sh/zrq9uorr1vbsm46/AACbF_Xk5wWWLRVZ90o1GPSHa?dl=0