<p>From the earliest days of the Cold War, bombers had stood alert not merely at runway's end but in the stratosphere, where B-52s flew back and forth with 'live' hydrogen bombs in their bays. The handling of atomic weapons was deemed very sensitive, and only elite crews flew these 'Chrome Dome' missions. Still, for more than 15 years, it was taken for granted that it was acceptable and safe to fly around with The Bomb on board. Even as the United States began its relentless descent into the Vietnamese quagmire, airborne alert missions pressed on.
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<p>In January 1966, a B-52 Stratofortress collided with a KC-135 Stratotanker during a high-altitude refueling and both crashed near Palomares, Spain. There were four survivors and seven fatalities. Some radioactive material was released when the TNT triggers of two of the four weapons aboard the B-52 exploded on impact. All but one of the hydrogen bombs was recovered immediately. The search for the lost weapon took two months and was concluded at a water depth of 2,850 ft (868 m) in the Mediterranean using an experimental submersible. Many other events occupied the news—the previous year, the massive American build-up in Vietnam had become a fact of life—but world attention was glued on the Palomares until 7 April when the last of several attempts recovered the missing weapon.
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<p>The 'Palomares incident' brought an end to the practice of aircraft flying with nuclear weapons on board during peacetime. 'Chrome Dome' missions ended. Bombers continued to sit on nuclear alert, ready to go, loaded up with hydrogen bombs, but none ever flew again. The ICBM continued to become more numerous than the manned bomber. Lyndon Johnson's Defense Secretary Robert S. McNamara went ahead with plans to retire a major part of the SAC bomber force, including nearly all B-52s, by 1971. The plan was 'stretched out' when control of the White House shifted in January 1969. It became moot several years later.
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<p>Richard Nixon's advisors kept the B-52 alive and invested in the General Dynamics FB-111 as an interim part of the SAC arsenal, but the dominance of the bomber was becoming past tense. In 1969, US troop strength in Vietnam reached its peak of 545,000. It was an intolerable situation to a nation which had been promised 'guns and butter' and was now seeing 200 Americans a week come home in body bags. The nation was also seeing civil protest grow into riots in its streets.
