I am a forwarder who uses flight aware for tracking flights which have our shipments on them. It would be convenient to have the e-mail notifications have an ability to set user specifics remarks so that we might include shipment specific details on the notification. Other customers might find this useful as they could tailor a notification to include a flight with a client or a loved one on board so that they know that this is the flight that would have their person of interest. I am not sure if this is possible, but its just a suggestion that might be implemented. Perhaps it could be a perk offered at a paying subscription level to justify the expense of programing and modification to the site.
In any event it would be a nice feature and allow us to not get flights confused as we track so many some days.