Federal law does not mandate a no nut policy. No accommodations are legally required for people who have nut (or other) allergies. In fact, there are fewer protections and policies in place to guard against allergic response than in previous years. The reason is simple: with more people now bringing their own food on board, airlines cannot ensure a nut-free environment.
AA does not serve peanuts, but they do state their in-flight food selections do have nut products in them. Also, since passengers are allowed to bring food, peanuts may come into the plane that way. They encourage their passengers with allergies to take all necessary precautions to protect themselves when in-flight.
United Airlines and Continental
You really have to dig on their website to find their nut policy. Once you do, it’s basically the same as AA. They do not serve prepackaged nuts, but they cannot guarantee a nut free environment. Since Continental and United have merged, they share the same policy.
They do not make accommodations for peanut-free snack requests and recommend that passengers bring their own snacks if they have dietary limitations.
What can you do?
When you get on the plane, ask to speak to the captain. Make sure he or she knows they are carrying a passenger with a significant food allergy. If a passenger goes into anaphylactic shock, the Captain will make an emergency landing. The flight crew should be aware of the possibility. You can always ask your travel agent to make a note of the severe allergy in your fight record. If a buffer can be created around you, they may do it. You can also switch seats on the plane to a more isolated location if one is available. Work with the cabin attendant toward that end. And be sure to carry your EpiPen! Keep it handy, where it can easily be reached. Protect yourself and your loved ones first.
Source: UA, AA, USAirways, eHow