Officially, aliens have never existed but flying saucers very nearly did. The National Archives has recentlypublished never-before-seen schematics and details of a 1950s military venture, called Project 1794, which aimed to build a supersonic flying saucer.
The newly declassified materials show the U.S. Air Force had a contract with a now-defunct Canadian company to build an aircraft unlike anything seen before. Project 1794 got as far as the initial rounds of product development and into prototype design. In a memo dating from 1956 the results from pre-prototype testing are summarized and reveal exactly what the developers had hoped to create.
The saucer was supposed to reach a top speed of “between Mach 3 and Mach 4, a ceiling of over 100,000 ft. and a maximum range with allowances of about 1,000 nautical miles,” according to the document.
If the plans had followed through to completion they would have created a saucer, which could spin through the Earth’s stratosphere at an average top speed of about 2,600 miles per hour. Wow. It was also designed to take off and land vertically (VTOL), using propulsion jets to control and stabilize the aircraft. Admittedly the range of 1,000 nautical miles seems limited in comparison to the other specifications – but if you’d hopped on the disk in New York it could’ve had you in Miami within about 24 minutes.
The document also hints that the product development seemed to be going better than planned; “the present design will provide a much superior performance to that estimated at the start of contract negotiations.”
It begs the question – why was the project dropped? Why aren’t wars being fought with flying saucers? The cost of continuing to prototype was estimated at $3,168,000, which roughly translates to about $26.6 million in today’s money and wouldn’t have been an insane price for such advanced technology. The problem with the other flying saucers developed under the same program (see video) is pretty clear. They didn’t get anywhere near 100,000 feet in altitude, more like five or six if you were lucky – so the military finally pulled the plug in 1960.
http://www.wired.com/dangerroom/2012...8&pageid=93368

Recently declassified records from the Aeronautical Systems Division, USAF (RG 342 – Records of United States Air Force Commands, Activities, and Organizations) reveal some surprising, perhaps never-before-seen images: 
USAF Project 1794

The above illustration was discovered in the pages of a document titled “Project 1794, Final Development Summary Report” (d.1956) The caption reads “USAF Project 1794”. However, the Air Force had contracted the work out to a Canadian company, Avro Aircraft Limited in Ontario, to construct the disk-shaped craft. According to the same report, it was designed to be a vertical take-off and landing (VTOL) plane designed to reach a top speed of Mach 4, with a ceiling of over 100,000 feet, and a range of over 1,000 nautical miles.

Fig 1 Cutaway of Aircraft Structure

Fig 2 Cutaway of Aircraft Structure


Curiously, these pictures bear a strong resemblance to ‘flying saucers’ in popular science fiction films made during the years these reports were created: 1956 and 1957.
http://blogs.archives.gov/ndc/?p=426