I was very lucky when I visited Dubai that the Jumierah Hilton let me check in at 6am! I'd arrived on a very early flight and stupidly had not booked the night before.

I actually arrived at the hotel at 04:30 but they said they had to wait til 6am for the computer system to recognise it was the next day and check me in. I was Diamond at the time, and the staff could not have been more helpful.