Jock,
You are into a can of worms with your question - depends what sort of diving you are doing.
If you are a recreational diver, then the stated minimum is 12 hours from Diving->Flying - though we generally tell students that 24Hours is a safer minimum.
Now if you are in the technical diving realm it all depends on depths, bottom times and also the big deciding factors of what gas mixes you have been using. Now you see the problem!! If you you been breathing one gas, say Air or EANx during a dive then generally your dive computer will recommend a 'No Fly' time, some more complicated computers (such as Cochran Nemesis II) can cope with 3 different gas mixes.
Maybe there are some divng docs on the board who may be able to give a bette insight into the technical side. Bubble theory is a big discussion topis in the magazines and boards at the moment.
Julian.
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Live fast..dies young...leave a good looking corpse!