Followed us over Greenland. Many changes in direction and altitude
I'm a pilot for an international airline.On this day we flew from Frankfurt/Germany to Vancouver/Canada. We were three pilots on this flight and the captain made a break at this time. 25 minutes after we passed the cost of Greenland on an altitude of 37.000ft, I saw a shine point right in front of us which was coming into our direction. It got bigger and bigger. I wasn't sure if I hallucinated, so I asked the second First Officer if he is able to see the object and he also saw it. We both were a little bit shocked but we couldn't report the sighting, in fear of losing our jobs. The object was bigger then our B747-400 and made significant movements. We couldn't directly here the sound but we heard weird noises via radio. It sounded like someone is cracking his bones. After probably three minutes the object made a extremely fast vertical climb and was gone in just a few seconds.