As of Dec. 2013, USAir and American Airlines have merged. Please see the policy below.
Per their website:
American recognizes that some passengers are allergic to peanuts and other tree nuts. Although we do not serve peanuts, we do serve other nut products (such as warmed nuts) and there may be trace elements of unspecified nut ingredients,including peanut oils, in meals and snacks. We do not have in place procedures that allow our flight crews not to serve these foods upon request of a customer. We do not provide nut “buffer zones”. Our planes are cleaned regularly, but these cleanings are not designed to ensure the removal of nut allergens, nor are our air filtration systems designed to remove nut allergens. Additionally, other customers may bring peanuts or other tree nuts on board. Therefore, we cannot guarantee customers will not be exposed to peanuts or other tree nuts during flight, and we strongly encourage customers to take all necessary medical precautions to prepare for the possibility of exposure.