Come on chaps, get real. The one thing that we do know is that terrorists are devious. They have gone to enormous ends to get their plots to work. So, is it really out of the question that one of the groups wouldn't put forward a follower to fly for, say, a Middle Eastern airline so that they can act in exactly this way? If pilots were not subject to the same security as everyone else then this would be potentially successful, surely?
Of course, that pilot could take over the aircraft and commit another 9-11. However, aircraft need pilots, so there is little that can actually be done about that threat beyond the obvious. However, the scenario that I outlined, which is surely not so far-fetched given the nature of other atrocities, can be eliminated, and thus there is some logic in so-doing.
I stress that I do not agree with the current security arrangements - the risk of being killed in a terrorist incident in the UK in the last five years is about 1:5 million, which is tiny compared with other risks, and we are losing a huge amount to try to mitigate this, which is a nonsense. However, once a decision has been made that screening is necessary there is no logic in allowing a particular group to avoid it en mass, from a risk management perspective at least.