Today In History

Wired has it, for January 17, 1966:

A U.S. Air Force B-52 bomber collides with its refueling tanker jet in mid-air over the Spanish coast. Its four hydrogen bombs fall to earth near the fishing village of Palomares. The bomber collided with the KC-135 tanker at 31,000 feet. Exploding fuel completely destroyed the tanker, killing all four crew members. The B-52 broke apart, spilling its payload — four Type B28RI hydrogen bombs equipped with 1.45-megaton warheads. Three hit the ground near Palomares while the fourth fell into the Mediterranean Sea.
Three members of the bomber’s seven-man crew were killed in what became known as the Palomares hydrogen bombs incident.
Although the conventional explosives contained in two of the four bombs detonated, there was no nuclear holocaust. But there was radioactive contamination around the crash site, with plutonium scattered over 2 square kilometers. Around 1,750 tons of earth was excavated and shipped to the United States for disposal.
The bomb that landed in the sea went missing for 80 days and became the object of an intensive search by the United States, which was afraid the Soviets might try to recover it.

Zoinks, that's a little too close for comfort.