A US Department of Defense contractor's tantalizing encounter with a giant, glowing UFO has sparked 10 years of research and two patents inspired by his encounter.

Three witnesses, including that Pentagon engineer, report that they captured electronic evidence of a 'barbell' UFO, half the length of a football field, that glowed an eerie 'indigo' blue.

The craft, they said, flew silently over an old logging road in southwestern Ontario, Canada, on August 28, 2013, near where the trio had camped for a hunting trip.