Even though I know this, smelling peanuts (especially peanut butter) makes me intensely uncomfortable and I'm happy they're not served on most flights anymore. I'm not trying to ban anyone from taking their own peanuts on the flight (although I wish they wouldn't) but not needing to worry about it coming from the airline is a huge load off my mind.

Also, thinking as the airline, I'd do anything possible to avoid causing anaphylaxis on a flight, starting by simply removing common allergens from the menu. In the modern world, pretty much the only times an anaphylaxis attack would actually threaten my life would be camping in the wilderness and on a flight. Anaphylaxis has a great survival rate if you have an epipen and can get to a hospital quickly, and if you can't it's all down to how bad your allergy is and what meds you have available. Maybe I'm stupid but I don't bring on a flight the steroids that I'd bring camping, and I doubt the airplane has a supply either.