John Powell, 56, claims an unusual silver orb was following the military craft as it came in to land at the base.
The retired school teacher was gardening at his home in nearby Westbury when he noticed the sun glinting off the circular surface.
“I don’t believe in things from outer space but that thing was definitely tracking the plane,” he said.
“My neighbour was in the garden at the time and I wanted to shout to them, but I didn’t want to say ‘there’s a flying saucer in the sky’ so I didn’t say anything in the end.”
Mr Powell, who taught computer sciences in Belfast for 30 years, added: “I thought at the time this is too good to miss but I didn’t think the picture would come out as good as this.