you have asked an interesting question. peanut allergy is one of the most severe food allergies. it can cause itchiness urticaria swelling eczema sneezing asthma abdominal pain drop in blood pressure and cardiac arrest. it may even result in anaphylactic death if not controlled in the right time. the routes of exposure of the allergen are mostly the accidental ingestion of peanuts or pb by the concerned person (who is hypersensitive to peanuts). air-borne particles in a farm or factory or crushing environment may cause respiratory symptoms in allergic individuals. however the odor of peanut butter or its mere proximity have not produced any allergic symptoms in various studies conducted. hence answering your questions. it is safe to carry peanut butter in plane. if you are carrying it as part of hand baggage (cabin baggage) make sure it is packed properly in a colored container. this is just to prevent any psychogenic allergic symptoms in those susceptible individuals who may see the butter and develop allergy (however such psychogenic reactions are very rare but still documented in studies). since the pb as such is not an allergen by sight/proximity/odor a susceptible person need not take extra precautions to avoid allergy when someone else is carrying pb. however since psychogenic reactions can occur it may be advised that such a susceptible person may change his seat to another seat away from person who is carrying peanut butter. for further information consult an allergic specialist online --> <link>
does peanut butter pose any allergy threat?