It seems that back in 1969 former US president Jimmy Carter sighted an unidentified flying object:

The object stood still in the sky for a period of ten or twelve minutes, slowly changing its color, size, and brightness, and then gradually retreated into the distance, disappearing from view. Carter estimated that the object, at its closest, was some 300 to 1,000 yards away.

But it turns out that it was probably the planet Venus.

Straight Dope: Did Jimmy Carter really see a UFO?