I went to all but 3 aways last season... From what I recall... We took 2800 instead of 3000 to Swansea in the capital one cup 2nd leg when already 2-0 down. That was a wednesday night and the weather was atrocious. Took me 6 hours to get there.
United away in the FA cup we took 5000 instead of 6000. It was a bank holiday sunday with no trains running to Manchester or back. Plus it was Mothers day. And we only got the tickets one week before the game.
We took 2800 instead of 2900 to Sunderland.
We took 2800 instead of 3000 to United in the league. We had played 66 games before that covering Europe and Japan. Plus Amsterdam was around the corner.
Last one we didn't sell out was Middlesbrough away in the FA Cup. We took 2100 instead of our 2400 allocated for a Wednesday night game in Middlesbrough.
At home we sold out every league game and every FA cup/Capital one cup/Champions league but we didn't sell out all the europa league home games.
We have one of the best supports in england. And one of the best away supports for sure. Matched only by United, Liverpool, Leeds, Arsenal and at a stretch Newcastle.