Aurora is the name given to a rumored advanced U.S. spyplane. It would be the successor to the SR-71 Blackbird. Many conspiracy theorists as well as area 51 watchers claim to have seen this thing. Some facets of the reports do remain consistent, however.

Screeching noise. The aircraft is said to make a 'screeching' or 'screaming' noise, as opposed to the normal roar of a jet engine. One possible explanation for this is that the Aurora is equipped with a pulsed SCRAMjet, which (experts claim) would produce this sort of sound. It's sort of a higher-frequency and louder version of the sound produced by the V1 Buzzbomb of World War II fame.

Doughnuts-on-a-rope. Several observers have described a contrail which rather than being the normal linear cloudlike formation has, in addition, toroid clouds of smoke/vapor around the line at regular intervals. This, too, points to some sort of pulsed engine. One gentleman who claims he saw a 'black triangle' zip across and above the flight path of his airliner actually took a photo which does show such an exhaust trail.

Extremely fast. This would make sense. It has been hypothesized that the Aurora may be akin to the never-built Nazi 'Victory Bomber' in that it 'skips' across the top of the atmosphere, allowing it to travel without the problems of friction heating or drag. This is not without operational precedent; the X-15 actually flew high enough to be considered a spacecraft, using reaction thrusters for attitude control until it re-entered thicker air.

Does this plane exist? We don't know, yet (well, at least, I don't!). However, I consider it highly likely there is some sort of replacement for the SR-71 in advanced stages of development, if not actual operational use. Some circumstantial evidence for this:

  • The Air Force not only acquiesced to the deactivation of the SR-71 fleet, they actually turned down funding at a later date to reactivate several of them.
  • Satellites do not have the flexibility of a manned aircraft in obtaining imagery; you're restricted by orbital dynamics as well as the scarcity of resources - spysat time is one of the scarcest resources out there.
  • The F-117 Stealth Fighter was actually in operation for several years at Tonopah AFB (and tested at Area 51?) before being revealed to the general public. If a reasonably large force of combat aircraft can be 'hidden,' why not a smaller number of reconnaissance planes?
  • My favorite. Several years ago, there was a funny incident concerning FAA NOTAMs (Notice to Airmen). This is the central database of 'warnings' or informational announcements that might affect the safety of aircraft operating in the U.S. Anyhow, for a couple of days (apparently; I've seen what purports to be a copy of this but did not see it myself) there was a notice filed which warned of 'multiple unscheduled high-mach transits over the Los Angeles Basin at flight level 750 and above.' Flight level 750 is 75,000 feet, well in excess of the operational ceilings of even most fighter aircraft. However, a couple of days later, this notice vanished from the NOTAMS database, with another notice appearing with its number.
In addition to this, I have recollection of but no reference for an article which reported that careful examination of the aggregated seismic data for the Los Angeles basin showed a clear set of sonic boom trails which came in from the Pacific at various angles...all of which, if extended out in a straight line, terminated somewhere near Groom Lake and Area 51 - a famously secret U.S. Air Force facility.

Who knows? It's fun to watch for small things and try to piece them together.