Its not just a question of allergic reaction; the fatal dose for most anaesthetics is not much higher than the standard dose; thats why they have Anaesthetists/Anaesthesiologists to closely monitor the patient. In any forseeable situation in an a/c you could not knock out all the pax rapidly without killing some. As for anaesthetic darts the situation is as bad or worse; the reason why the animals shown anaesthetised by dart take several minutes to react is due to a compromise between having the animal rapidly unconscious and having it dead. Most anaesthetic gasses are also extremely flammable; there have been cases of patients exploding on the operating table.