Operation Skyshield

Operation Skyshield was a series of three large-scale military exercises conducted in the United States in 1960, 1961 and 1962 to test the North American Aerospace Defense Command (NORAD) defenses against Soviet air attack. The tests were intended to ensure that any attacks over the Canadian border or coastlines would be detected and subsequently stopped. The results of the tests were classified until 1997, due to fears that they could be used by the Soviet Union in order to more effectively engage the US in the event of World War III.

In these exercises, all US civil air traffic was grounded (sometimes up to 12 hours). They involved 6,000 sorties flown by air forces from the US, UK and Canada, simulating Soviet fighter / bomber attacks against New York, Chicago, and Washington. This made it the largest military aviation exercise ever held.

In reporting on the September 11 attacks in 2001, these exercises were often overlooked, with news agencies reporting that the similar, but unplanned, evacuation of US airspace during that incident was the first ever clearing of US airspace of all civilian aircraft.

Operations
Sky Shield I included an "attack" by eight Royal Air Force (RAF) Vulcan B.2 bombers. Four aircraft attacked from Scotland and four from Bermuda. The first "casualty" of the exercise was an RAF Vulcan which was intercepted by a McDonnell F-101 Voodoo 56,000 ft above Goose Bay, Labrador. Despite this, the Vulcans achieved unprecedented survivability with seven of the eight British bombers managing to reach their targets and return to Stephenville, Newfoundland unscathed. Their effectiveness in the exercise was largely due to the advanced Electronic Counter Measures systems on these aircraft (three of the southern route bombers putting up a wall of interference while the fourth made an attack ) and the Vulcan's famed and unique maneuverability amongst strategic bombers,
 * Sky Shield I (1960)

During Skyshield II, the RAF Vulcans participated again, four from 27 Sqn (serials XJ824, XH555, XJ823, and one other), again flying from Kindley Air Force Base, Bermuda, and four aircraft from 83 Sqn flying from RAF Lossiemouth, in Scotland. They simulated Russian heavy bombers operating at the highest altitude - 56000 ft; above the United States Air Force (USAF) B-52s at 35-42,000 ft and the lower level B-47s. One 27 Sqn Vulcan, flying from Bermuda, successfully evading the defending Convair F-102 Delta Dagger interceptors, covered by the other three jamming operations, tracked round to the north, landing at Plattsburgh Air Force Base, New York. The northern force attacking in a stream reported a single instance of radar contact by an interceptor and all four landed in Newfoundland.
 * Sky Shield II (1961)

During this exercise, there were eight casualties, all from the crew of a B-52 lost in the Atlantic. On 15 October 1961, a search triangle 600 miles from New York was set up looking for the missing crew. A US Coast Guard (USCG) cutter reported seeing an orange flare at 12:15am on 17 October, but the eight crew members were eventually presumed lost at sea.

Sky Shield III, held in September 1962, was North America's first test of procedures for clearing national civilian air traffic at short notice, such as would be done in the event of a Soviet attack. Hundreds of USAF trainers were used to simulate normal civil traffic levels and routes.
 * Sky Shield III (1962)

News coverage
The penetrations by RAF Vulcans was first reported in a British newspaper, the Daily Express, in January 1963. It was initially strenuously denied by the United States Department of Defense, which stated "that British aircraft last took part in a Strategic Air Command exercise over the United States in the Autumn of 1960". In a later statement, Eugene Zuckert, Secretary of the USAF, said the report was; "completely without foundation". The Chicago Tribune newspaper reported; "We do not know whether the Royal Air Force leaked the story in order to show up the Kennedy administration because of its decision to scrap the Skybolt air-to-ground missile".