It is a flash mob by Malaysia Airlines at KLIA on 14 January 2012. It is superb superb and I wish I was there to watch the performance.
I was just browsing randomly on sixthseal.com and I saw his entry on it, which I could not resist to reblog it. It is like a musical show as he said and I personally think it is even quite a touching one. The video is nicely done too.