A friend was on a flight, and spotted this:

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DSC00984 on Flickr - Photo Sharing!)


The missing fairing worried him a bit, so he queried it with the cabin crew who said the flight deck were aware, and unworried.
Fair enough, but I was curious. I presume that the fairing would need to be signed off by an engineer. Are there some bits that it's perfectly OK to fly without?
Cheers