dmpaq20:Al you need to do is carry them on. You are not required to remove or dissassemble anything.
Not strictly true, if its a big heavy light in post 11/9 paranoia it can be classed as a weapon and refused.
Plus the weight of my dive light takes up more than 50% of my already tiny baggage allowance. All ive ever been asked was to ensure it cant turn on in flight - i do this by reversing the battery and have had no problems in any of the countries after doing that.