I'm new to the forum and don't really understand where this thread will show up, but hopefully it will be with the other comments about Janet aircraft.
First of all, Janet's have tail numbers. I've photographed them from the Island Tower at the Tropicana Hotel.http://www.lazygranch.com/janair.htm
Janet aircraft are civilian, and thus have N-numbers, as listed on the link above. If you go tohttp://www.lazygranch.com/janet_audio.htm
you can hear scanner audio of these planes. Some of this audio is from Janets on the ground at Groom Lake, not all that easy since the base is in a valley. I go to a nearby hill that doesn't quite have line of sight but is about as good as can be done just by driving. Then I use antennas cut just for the tower (military and civilian frequencies).
I haven't photographed them from the ground in quite some time. However, I would think photographing the Janets and their terminal from the long term parking garage would not get the TSA on your case.
The Tropicana is probably going to be sold in the next few months. A few people I know into Area 51 have done their pilgrimage to photograph the terminal from the Trop. You ask for a room in the Island Tower, facing the airport, as high as possible. Nobody even bats an eyelash at the reservation desk as this request has been done a few time before. Janets start to fly damn early. If you are a Vegas party animal, you will probably sleep through all the Janet activity.
I think JANET is the secret airline that transports people that work on Area 51. There is a show about on TLC I think and they sho wit every once and a while. Janet stands for Just Another None Existent Terminal. Its a wierd thing and they Operate Boeing 737-100s and 200s. There red and white without a tail number. I think you can get on the frequencie somehow. And they take of from Las Vegas. I hoped that helped you abit and I'll try to answer any more questions, and you cant track JANET flights.