Operation Chrome Dome was a United States Air Force Cold War-era mission from 1961 to 1968 in which B-52 strategic bomber aircraft armed with thermonuclear weapons remained on continuous airborne alert, flying routes that put them in positions to attack targets in the Soviet Union if they were ordered to do so. The exact routes varied by year, but in general there were routes that went to positions over the Canadian arctic, Alaska, Greenland, and the Mediterranean Sea. Many American Air Force bases in the 1960s allocated at least one bomber crew to "Chrome Dome" duty on a regular basis, and many other bases, including foreign bases, were involved in the refueling operations. Over the years the mission involved overflights of American, Canadian, Danish (Greenland), and Spanish territory, among others. The goal of "Chrome Dome" was to keep a number of nuclear-armed aircraft in a position to help guarantee nuclear retaliation against the Soviet Union in the event that the latter was able to destroy the majority of US nuclear weapons still on the ground. The operation also ensured that Strategic Air Command bomber crews had experience with airborne alert procedures so that, in the event of heightened concern, the number of patrolling bombers could be increased dramatically. Several high-profile nuclear accidents were associated with the "Chrome Dome" program, including the accidental release of nuclear weapons on foreign territory, and the mission ended following one such accident, the 1968 Thule Air Base B-52 crash.
Background: airborne alert
After the Soviet Union's launch of Sputnik 1 and Sputnik 2 satellites in 1957, US military planners feared that intercontinental ballistic missiles could under some circumstances destroy the bomber forces of the Strategic Air Command (SAC) prior to their taking off. General Curtis LeMay had, prior to this, worked to reduce the ground-based alert time for SAC's B-52 bomber forces to 15 minutes, but the new SAC commander, General Thomas S. Power, pushed to augment this with a full airborne-alert program, in which some portion of the American B-52 bomber force would be airborne and armed with nuclear weapons 24 hours a day. This would make it impossible for an incoming attack to destroy the entirety of the US continental nuclear forces, guaranteeing the possibility of a retaliatory strike. The initial pilot program in 1958 saw one bomb wing launching a combat-ready B-52 every six hours. Over the years, this expanded to SAC launching 12 sorties per day by late 1961. By 1960–1961, the alerts followed "ladder" routes that went from the United States up into the Canadian arctic. Over the course of 1961, there were several distinct operations that gradually increased the number of planes involved. The purpose of all of these named missions was "indoctrination": while acting as an active airborne alert operation, they were also meant to be training missions for a more general airborne alert with many more planes. The ultimate plans called for the ability to maintain at least 1/16th of the entire SAC bomber forces in the air at any given time in a period of high alert. The operations of 1961, each using 12 bomber sorties, were: "Cover All" (15 January–31 March), "Clear Road" (1 April–30 June), "Keen Axe" (1 July–30 September), and "Wire Brush" (1 October–5 November). "Wire Brush," for example, involved at least 11 B-52s, each launched from a different American airbase, traveling along 6 different routes over Canadian airspace. During Operation "Cover All", there were at least two serious accidents involving B-52s and nuclear weapons, one near Goldsboro, North Carolina, and another a few weeks later near Yuba City, California. As the number of bombers increased, the route became congested in a way that made it clear that getting to 1/16th airborne alert status, or an even more ambitious 1/8th status, would jeopardize flight safety. Operation "Chrome Dome" was conceived of as a revision to the original "ladder" routine, as well as an attempt to make the airborne alert program a "regular" one, rather than the short-term alert programs that had preceded it. The new plan would use two routes, one circumnavigating Canada known as "North Country", the other traversing the Atlantic to the Western Mediterranean Sea (known as "Mail Pouch"). These planes would be refueled in-flight by KC-135 aircraft operating out of bases in the northeast United States, Alaska, and Spain. "Chrome Dome" was approved by the Department of Defense and began in November 1961, with four strategic wings and two bomb wings flying one sortie a day, and one bomb wing flying two sorties a day, on the northern route, and four strategic wings flying one sortie a day on the southern route. Two of these 12 bombers per day were sent to monitor the BMEWS facility near Thule, Greenland. After several weeks of operation, the planners judged "Chrome Dome" a success in addressing the problems created in previous operations. It was explicitly planned that, in times of high alert, the number of B-52s on the "Chrome Dome" routes could be increased far above the twelve daily flights. "Chrome Dome" is the best-known of the SAC airborne alert programs, in part because several high-profile "Broken Arrow" nuclear weapons accidents became associated with it, including the 1968 accident at Thule which ended the program. But it was not the only such program; it existed side-by-side with other, more-temporary airborne alert programs with names like "Hard Head", "Round Robin", and "Butterknife". As an official history put it, "Operation Chrome Dome was only the most dramatic and best known program requiring that nuclear weapons be kept aloft."
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