Six Top-Secret Aircraft Mistaken for UFOs

Spy and stealth planes - some with bizarre, bat-shaped wings, others with triangular silhouettes that imply otherworldly designs - have long generated UFO sightings and lore. And official denials feed rumors that the government isn't telling us about alien ships.

The CIA estimates that over half of the UFOs reported from the 1950s through the 1960s were U-2 and SR-71 spy planes.

At the time, the Air Force misled the public and the media to protect these Cold War programs; it's possible the government's responses to current sightings of classified craft - whether manned or remotely operated - are equally evasive.

The result is an ongoing source of UFO reports and conspiracy theories.

Here are the Earth-built craft that likely have lit up 911 switchboards over the years.

1. RQ-3 Darkstar

Manufacturer: Lockheed Martin/Boeing
First Test Flight: 1996
Deployment: None (it was canceled in 1999)
Declassified: 1995
Size: 15 ft long; 69-ft wingspan
Performance: 288 mph (cruising speed); 45,000+ ft (max. alt.)

UFO Link: The official life span of this unmanned spy plane was brief and disappointing, with a crash and a program cancellation after just three years. But in 2003, Aviation Week reported that a similar stealth UAV was being used in Iraq - fueling speculation that the government scrapped the craft publicly only to secretly resurrect it for clandestine missions.

2. U-2

Manufacturer: Lockheed Martin
First Test Flight: 1955
Deployment: 1957 to present
Declassified: 1960
Size: 49 ft long; 80-ft wingspan
Performance: 410 mph (max. speed); 85,000 ft (max. alt.)

UFO Link: Designed for high-altitude reconnaissance, the U-2's long, gliderlike wings and silver color would have been notable to observers on the ground and in the sky. In the 1960s the airplane was painted black to avoid reflections. The U-2 is also famous for being among the first classified planes to be flown from the Air Force's secret test facility at Groom Lake, Nev. - aka Area 51.

3. SR-71 Blackbird

Manufacturer: Lockheed Martin
First Test Flight: 1964
Deployment: 1966 to 1990, 1995 to 1998
Declassified: 1964
Size: 107 ft long; 56-ft wingspan
Performance: 2432 mph (max. speed); 85,000 ft (max. alt.)

UFO Link: The tailless spy plane has an even more unusual cross section than the U-2. This Area 51 alum was briefly reactivated in the 1990s, and rumors of a followup - the now-legendary Aurora project - have supplied both UFO believers and skeptics with a possible source of unexplained sightings.

4. P-791

Manufacturer: Lockheed Martin
First Test Flight: 2006
Deployment: Unknown

UFO Link: Plane spotters' photos and videos blew the top-secret cover off a 5-minute inaugural flight in Palmdale, Calif. The hybrid airship - it uses gas and a wing shape for lift - fuels speculation that classified airships quietly roam the night skies.

5. F-117A Nighthawk

Manufacturer: Lockheed Martin
First Test Flight: 1981
Deployment: 1983 to 2008
Declassified: 1988
Size: 107 ft long; 56-ft wingspan

UFO Link: This long-range stealth fighter, which could stay aloft indefinitely thanks to midair refueling, remained classified through much of the 1980s during test flights at Tonopah Test Field Range in Nevada, 80 miles from the legendary Area 51 Groom Lake facility. Along with the B-2 Spirit, the batlike F-117A was a perfect candidate for triangular UFO sightings.

6. B-2 Spirit

Manufacturer: Northrop Grumman
First Test Flight: 1989
Deployment: 1997 to present
Declassified: 1988
Size: 69 ft long; 172-ft wingspan

UFO Link: Although the long-range bomber was never a true "black aircraft," since it was displayed to the public approximately eight months before its first flight, an airborne B-2 is a UFO report waiting to happen. It looks like an alien craft from nearly any angle and specifically like a flying saucer when viewed head-on or in profile.