This happened around 20 years ago.I was flying from the U.K. to the US.I was sat in a window seat reading a book,my window was slightly forward of the wing.I glanced out of the window towards the 10 o’clock position and guessing at around 200 yards below the plane in this direction I saw what I thought was a sky scraper.I immediately thought I must have fallen asleep as we must be descending to land.I checked my watch and the in plane flight indicator and we were in the middle of the ocean and 30,000 feet above sea level.The object I can only describe as being shaped like the Empire State Building but completely jet black.Dull,not shiny no sign of any windows or any joins etc,completely smooth.It appeared to be stationary and was standing straight up (hence why I thought sky scraper).As there was nothing to compare it to I couldn’t be accurate to its size but it seemed huge to me.When I first saw it,it was partially covered in clouds around what I guessed to be its lower half, as the plane passed it by the clouds dispersed and the thing appeared to be very long,I don’t remember seeing the bottom of it.As the plane moved on I lost sight of it behind the wing.I was sat alone and as I looked around to see if anyone else had seen this thing,the passengers around me were asleep. At the time of the sighting dawn had just broken the sky was clear apart from the aforementioned wispy clouds.I don’t drink and have never taken any drug stronger than an aspirin!. When I landed I told my girlfriend who I was meeting up with and on my return to the U.K. I told my best friend what I’d seen. Then for a number of years I inexplicably forgot all about this event. When I re remembered the incident I asked my friend and girlfriend if they remembered me telling them about it.They both clearly remembered me telling them. To this day I still have no idea what it was that I saw.If it’s something we’ve built then it’s still top secret 20 years later as I’ve seen nothing remotely similar.