We have been on flights were there was a severe peanut allergy where no nuts were served and passengers were asked that no peanuts be eaten on the flight by anyone. Also, we've heard of flights were airlines have created a buffer zone around a passenger with a severe peanut allergy (usually 3 rows in front and 3 rows behind) and anyone in that zone was asked not to eat any nuts. Just something to keep in mind.
Both of these happen when I fly on a Canadian airline. I am anaphylactic to tree nuts (TN) and peanuts (PN) and in the past have reacted to a large amount of peanut shell dust in the air (at a restaurant that had the shells all over the place; this was when I discovered the "hard way" that the peanut allergy included an airborne component if there was enough in the air).
As required by the (Canadian) airlines (WestJet, Air Canada, Porter), I notify the airline be phone well in advance of the flight, usually just after purchasing the ticket. Depending on the airline one deals with a normal customer service agent or is transferred to the airline's medical department.
If asked, Canadian airlines are required to create a multi-row buffer zone around the TN/PN (as appropriate) allergic passenger's seat in which the passengers in the zone are directly spoken to by the flight attendant and asked to not consume TN/PN-containing products during the flight. Also, no TN/PN products will be served either in the zone or on the plane. If another passenger in the zone insists on consuming a TN/PN product, they will be moved to a seat outside the zone.
All three airlines have also told me that they would prefer to make a plane-wide announcement asking passengers to refrain from eating TN/PN products during the flight, although they have always asked if I was ok with that; the first time it happened I said it wasn't necessary, but the airline replied that they preferred to do it in order to reduce the risk, so I agreed. Since then I agree when ask.
The Canadian airlines will also allow me to preboard the plane so I can wipe down my seat area, prepare my other precautions, and settle.
Note that many/most US airlines do not have similar processes, or have a piece-meal of processes but not all of them, or hapazardly implement them. Some airlines (like American) are now downright hostile at times towards TN/PN allergic passengers and make no accommodations, including not allowing pre-boarding. In contrast, the Canadian airlines are REQUIRED
by regulation to have certain processes available/in place (including the buffer zone).
To the OP: Others have given some suggestions for trail mix alternatives, which could be a particularly good idea if flying on a Canadian airline since you may end up on a flight with someone like me where the announcements are made. One I really like is either of the two types of trail mix made by the
Enjoy Life company:
http://enjoylifefoods.com/our-foods/seed-fruit-mixes/ They are nut-free, gluten-free and free of the top allergens. Although I eat them because they are safe for me, I do enjoy them and highly recommend them. I have shared some of the Mountain Mambo (my favourite) one with co-workers who really really liked it and went and bought some of their own. Another snack I like when flying are granola bars (and there are many TN/PN-free options these days) and fig newtons (well, usually date newtons for me due to a dairy allergy).
Others have noted that jars of peanut butter fall under the 3-1-1 liquids rule (PB and things like jams are considered liquids/liquid-like for the purposes of the rule), so normal size jars have to go in checked baggage. Little single-use packets could go in carry-on though as long as they meet the 3-1-1 rule.
SW