For those of you "moaning"about stadium expansion. It is not as easy as piling up a few more bricks. Here in the UK we have a thing called "planning permission" which councils have to grant (United's council is NOT pro United). We also have a law called the "sunlight" law whereby people cannot block out others access to sunlight via windows, so the stadium can only be "so high".
Along the eastern side of the ground is a 5 or 6 line railway; to expand OVER this means building a massively strong tunnel which will not only support the superstructure but also take the vibration of trains going through all day and night. Also, there are residences opposite.
Behind the Stretford End was not United property until a few years back but they purchased several factories and levelled the ground, creating the players car park and the car parks for the season ticket holders. Theoretically this could be extended, but not by all that much. More seats means more cars.
The west side has a road which could be covered by then there is the canal, same situation as for the eastern side.
Sir Matt Busby Way. What do you do, knock down all the offices and the front, move the statues and build to the edge of the road, the cost outweighs the added seats.
You cannot go UP. Its hardly worth the price of the seats for the uppermost tiers now!!! If you go any higher, you will need a telescope to watch the game.
The only answer is a move.