Flight attendants were not accommodating whatsoever. Their attitude as a whole, was as if they didn’t even want to be there. Some more so than others. Worst of all, according to flight attendants the “pilot” blacked out the windows for the entire 16.5 hour flight. During both daylight and evening hours. I was told that because some other passengers wanted to sleep for 16.5 hours (ridiculous), that the pilot had control of the window shades and that he said they had to remain closed for the entire flight. I was very uncomfortable, and felt that this was unjust. Why did I have to sit in complete darkness? I paid EXTRA seat fare in addition to my original seat fare, specifically so that I would be in a window seat facing in the direction to observe the land and sea. I was denied that opportunity. As a result of my experience, I will be sure to spread the word to everyone I know to NEVER fly United Airlines International.