It looked like an orange flame flickering like a candle, but in all directions rather than a single direction as a candle flame would. It appeared to rise into the sky in the NW. At first I thought it was a firework, but it was a bit big for this and it just continued to rise without exploding, then carried on climbing towards the SE. All the time it was flickering with the orange "flames". There was not much traffic, but I could hear no sound from the object.

The object just kept flickering and moved in a at a steady speed. When it was clear it was not a firework, I thought it might be an aeroplane on fire, but it seemed to be "flying" well.

Clear night. Bright stars visible even in the city here. -1.5 degrees C, snow on the ground. It moved like an aeroplane would, climbing away on a set course. However, I could hear no sound and the flickering light was not like normal flashing navigation lights on an aircraft.