It all started in the late twenty second century. Also know as the Annihilation Period.
During the start of the 22nd century overpopulation had became one of the greatest challenges humans were facing at the time. As a result many governments got together and created the Alliance for CounterMeasures Against Overpopulation, also known as the ACMAO. The ACMAO funded many scientists to try and prevent the effects of overpopulation. These scientists were greatly successful. One scientists, known as Dr. Seinz, was able to bioengineer animals almost 6 times bigger than normal yet they required only half the amount of food and produced a fourth the amount of waste than regular animals. Another scientist, known as Dr. Muller, was able to create factories that were able to get rid of radioactive material safely, because of this nuclear power plants became the number one way to produce electricity. These two scientists were named as the greatest minds of their time. After their inventions were released there was a clear improvement on Earth for 10 years.
Newton's third law states that "for every action there is an equal and opposite reaction". At the same time as the scientists from ACMAO made their revolutionary inventions, an independent scientists, know as Dr. Vorgstun, felt that the only way to solve overpopulation was to decrease the population at that time by almost a half. In order to achieve his goal he created a virus that targeted anyone with O type blood which made up 45% of the population at the time. He completed his virus without anyone finding out and with unknown help he released the virus. Within weeks of the release population decreased by 40 percent, but this was only the start of a chain reaction; Dr. Vorgstun together with Dr. Seinz and Dr. Muller became known as the harbingers of death.
Due to the sudden drop in population size, many of the nuclear power plants became understaffed and within a couple weeks more than 75 percent of the factories failed causing radioactive leaks which made almost half of the habitable space on Earth unhabitable. Also, many of the factories, farms, and labs where the new bioengineered animals were kept scaped and started reproducing with wild animals and together with the radiation new mutations on animals started appearing creating large highly aggressive predators. Few areas were left unaffected by these problems, which caused large disputes between countries trying to claim these unaffected places. Wars broke out almost every where.
Luckily at the same time as Dr. Vorgstun completed his virus, another scientist, known as Dr. Green from ACMAO, had finish his new project. Large self-sustainable air ships able to house two million people each, known as airframes, he created this ships, since there was almost no more living places on Earth and many people lived in over crowded houses. He planned to mass produce them and make 500 in order to make space for 1 billion people to live on these flying ships, but then the virus hit and only 50 were able to be made before everything else happened. But nobody knew how to decide who would get to go on board, so wars continued to ravage the land, millions of lives list each day. many due to radiation poisoning, others caught by hordes of aggressive animals, and many due to the wars. Months passed without a single airframe going airborne.
The population kept decreasing at an alarming rate, finally the survivors made a cease-fire and came up with an agreement, 70 percent of the people on each ship would be composed of people ages 13 to 27 who were healthy, 20 percent would be doctors, scientists, engeneers, and other professionals that would teach the other 70 percent in hopes for them to make a better future, while the remaining 10 percentwould be any who wished to board, but they would work as laborers to support the rest, since it was a self-sustainable ship, only few workers were needed, many were happy to work to support the other 90 percent as long as they survived, but many chose to stay so that they wouldn't be separated from their families, since children and elderly were not permitted to join, because they were considered burdens. Within a couple weeks of the cease fire the people who would board each airframe was decided. After the airframes were airborne each became an independent nation.
These years were known as the Annihilation Period. it was a span of 20 years where population went from its all time high of 14 billion people to 98 million people alive confirmed in the airframes and an estimated 5 million left on Earth's habitable areas.
Less than 1 percent of the population survived those years.