In 1995, the then current X-Men creators started in motion what many thought would be unthinkable. Legion, Xavier’s son, traveled back in time with the intention of killing Magneto before he became a villain and could do any harm… but it all went wrong. Just as his future son was about to deal a killing blow, Xavier himself jumped in between Legion and Magneto. Xavier was dead… and the X-Men would never be the same again.
With Xavier gone, events unfolded much differently than that which we, the readers, had known. Only the time-displaced Bishop, a chronal anomaly himself, knew of what the world should be like. And so, what many think of as one of the greatest X-Men crossovers there has ever been, the Age of Apocalypse, was born … (Source UXN)
Read the breakdown on the original AoA on UXN. I find no reason to do something that they’ve already perfected.
The concept behind Flashpoint is picking up from the ashes of the final battles of the Age, and continuing that universe five hundred years later.
In X-men: Omega, there were some X-men mysteriously missing from the final battle. Storm, Exodus, Sabretooth, Wildchild, and Dazzler, for your information. When Blink saw the nukes coming she teleported herself out, and anyone else she could save, who happened to be Quicksilver. She teleported herself to the mansion, and then teleported out herself, along with those mysteriously missing X-men. She teleported them to the only safe place she knew; Antarctica. She knew Avalon was there and knew there was a chance. Herself and the other X-men made it to Avalon, and they stayed there, never having to fight battles again. The Age of Apocalypse was over.
There was also the Human Evacuation into space in X Universe. After seeing the nukes go off they also went to Antarctica. They thought they’d have to evacuate everyone to Avalon. When they saw that that was safe, they all ended up staying there. The world’s population existed in Antarctica from then on.
More so, After the Omega War as it was called, technology fell behind very much. The only remains of technology existed on the ships for the human evacuation. And there is only so much. Everyone feared another war, or the coming of another Apocalypse. Mutants and humans lived in peace. Also, November 17th was declared the new world wide Independence Day, the world was freed from the reign of Apocalypse. June 12th was made Memorial Day for those lost in the war, set on Magneto’s birthday.
The full history that followed can be found on the history page.