Some years ago I regularly flew in the observers seat of 747s as flight mech.More than once I flew with a particular captain whose behaviour led me to believe he was under the influence - the problem I had was that the other crew members seemed to accept his condition so I was reluctant to do anything. Finally one night as he was boarding an ops officer put his arm across the door and said to him "Not tonight captain" - that was the last we saw of him so someone must have decided enough was enough. We later heard that flight attendants had noticed a concealed bottle in the crew lavatory.