Suntan
Only four prototypes of the Mach 2.5 CL-400 or Suntan were ever built. This successor to the U-2 was to be powered by liquid hydrogen but it was deemed too costly to create an infrastructure for refueling around the world. The program was cancelled in the late fifties.
X-33(pop-ups)
While not fully an Area 51 only project, pop-ups like the X-33 and others are thought to have technology that was pioneered at Area 51. They often sport "new" technology that is already developed but yet has never been tested on known aircraft. In fact, some believe that the X-33 space plane is really the "white" version of the Aurora.
Black Manta
The TR3A Black Manta or Baby B-2 is widely thought to be the successor to the Stealth Fighter. Sightings around Area 51 are starting to be made of a smooth, rounded flying wing that is much smaller than a Stealth Bomber. Faster and more stealthy than the F-117, some believe it has already seen combat. It supposedly works in tandem with the Stealth Fighter, relaying target information.
Brilliant Buzzard
The Brilliant Buzzard or Mothership is thought to be a huge aircraft with a wingspan of two hundred feet or so which actually launches smaller reconnaissance craft. Sightings of this delta winged craft first began in the early nineties. Some believe that it and the Aurora are one and the same.
Stealth Fighter
Code named Senior Trend and known as the Hopeless Diamond, the F-117 Stealth Fighter was designed in the late seventies. So stealthy, aircrews sometimes find dead bats whose own sonar is so confused by the signal return from the F-117 that they crash into parked craft. The hero of the Gulf war, the Stealth Fighter is still tasked to take out the toughest targets and is only now becoming vulnerable to enemy radar.
Captured Soviet Craft
Area 51 is home to the Red Hat Squadron - fliers of captured or stolen Soviet craft. In fact, Groom Lake has so many Soviet craft that fliers often call it Red Square. Started in the 60's, the Red Hats have been key to improving kill ratios in Vietnam, the Gulf and Serbia. Craft include Mig 21s & 23s and the advanced Su 27.