Was taking my dog outside after work, noticed a very bright light in the north sky, immediately knew it was not a plane or satellite. Was to low and bright for a satellite and had no blinking lights for a plane, no noise and was flying over Billings Logan international airport so would of had to have some kind of directional lights or beacons. I ran inside and grabbed my phone and went back outside and that's when it turned to the west but wasn't really a turn but more of a long arch turn is the best way to describe it. I started to film it and zoomed in as far as I could, I moved my phone down twice to show the street light as a marker for how high and fast it was traveling. The second time I zoomed down on the street light the object dimmed but was in the same spot Traveling at the same speed but within 5 seconds it sped up so fast the light completely vanished and the first thought that went through my head was that it didn't seem to follow the curve of earth but seemed like it just went straight into space, the objects size did not change when the light dimmed just was not as intense and when it sped away it didn't just dissappear but could see it vanish as it got so far away in under 1-2 seconds at most. I tried to contact the airport to see if any tower control saw anything or if they had radar but could not get an answer.