Development of the E77 balloon bomb began in 1950. The E86 cluster bomb supplanted technologies such as the E77 balloon bomb. Batgirl then pushes Mary into a balloon bomb, killing her. At least three separate sets of tests were conducted with the E77 balloon bomb. The remains of a balloon bomb were found near McBride, British Columbia in October 2019. Near Medford, Oregon, a balloon bomb exploded in towering flames. Unbeknownst to the group, this was a dangerous Japanese incendiary Fu-Go balloon bomb. Following WWII, the United States developed the E77 balloon bomb based on the Fu-Go balloon.