Fifth Era

1942.
{From the UFO's point of view in the historical Battle of Los Angeles.)

They aren't worried about the anti-aircraft fire below. They're worried about the plutonium America is making. They wanted to make contact, but they decide to wait.

2026.
The UFO comes back. It parades over the entire country, evading our attacks. A computer genius that works for the White House sees it as something else.