1. Twin towers
2. Aircraft crashed into it and exploded
3. Stairs and elevators blocked by fire
4. Rooftop rescue by helicopter was impossible because of too much smoke
5. Building collapsed after a few hours
6. In the street, a wall of posters showing the missing victims
On a related note, there was a controversy in South Korea over a planned twin towers that looked like an exploding World Trade Center: http://www.bbc.co.uk/news/world-asia-16162789
Yeah, it's got that 9/11 vibe right down to the people stuck in elevators, the restaurant on the top, the top down shot of the firemen going UP the stairs while everybody else was going DOWN. It's obvious. Not that it bothered me in a "I'm offended" way, but it bothered me in that it took me out of the film because all of the similarities I couldn't help but notice. I believe that the film didn't show hoards of people buying up every single postcard with the buildings on it at the end like on 9/11 though. So there's that. :)
"Let's get out of here before one of those things kills Guy!"
Except that, while this movie was released in 2012, it was filmed in 2010 which was a year before 9/11 happened.
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They say marriages are made in Heaven. But so is thunder and lightning --Clint Eastwood