("Janet" is the call sign for the company that operates aircraft between Las Vegas and Groom Lake/Area 51).
They no longer fly the 737-200, by the way. They've replaced them with newer aircraft. I think they're flying the 737-500, now.
Probably 75% of the times my wife and I have gone to Frozen Fury, we are in a room at the MGM Grand that overlooks McCarran and can see them come and go. The EG&G terminal is located in the nearest corner of the airport.