This isn’t the oldest but it caught my attention:

74 BC – According to Plutarch, a Roman army commanded by Lucullus was about to begin a battle with Mithridates VI of Pontus when “all on a sudden, the sky burst asunder, and a huge, flame-like body was seen to fall between the two armies. In shape, it was most like a wine-jar, and in colour, like molten silver.” Plutarch reports the shape of the object as like a wine-jar (pithos). The apparently silvery object was reported by both armies.

Source: List of reported UFO sightings – Wikipedia

Opinion:

Was watching one of those UFO shows last night and saw the famed Phoenix Lights again. This time around it seemed more convincing than when they first hit the scene. Maybe I was just skeptical because there was so much web fakery back then, people using Photoshop for the first time to create things that were not real.

Now we know almost nothing on the web or on TV is real! But still, this video is compelling, especially since it was filmed with a relatively primitive video camera, way before cell phones could do video and mobile apps could add the fakery. Something authentic here, I feel.