In May 1956 the United States conducted the first airborne test of an improved hydrogen bomb.

Dropped from a B-52 bomber over the island of Namu in the Bikini Atoll in the Pacific Ocean, the successful test indicated that hydrogen bombs were viable airborne weapons and that the arms race had taken another giant leap forward.

The US began testing nuclear weapons at Bikini Atoll in 1946.  Early bombs were large, unwieldy and exploded from the ground.

The hydrogen bomb dropped over Bikini Atoll was far more powerful than those previously tested and was estimated to be equivalent to ~ 15 megatons of TNT. The explosive fireball measured was ~4 miles in diameter and its light brighter than 500 suns.