Delta Airlines updated its peanut policy on its flights to address those individuals flying with a peanut allergy: Delta Airlines: Peanut Allergy

A reminder to all: this is far different than a peanut free airline (which doesn’t exist). This is still an incomplete policy and not a reason to let your guard down. This does not prevent people from eating peanuts on board—it only prevents the airline staff from distributing peanuts. The buffer zone is relative to where you sit on your flight, and it is possible that during the last flight those same seats may have not been in a buffer zone and may have peanuts or peanut residue on them. You will still need to always wipe down surfaces, bring your epinephrine, bring your own food, etc.