Numerous sightings of unexplained flying objects and mysterious lights during the Vietnam War have been reported. Here is one veteran's opinion on the matter of UFOs.
"I can tell you UFOs are as real as your car you drive. I was in the Military in the Air Defense sector. I also served in Vietnam and UFOs were active there also. They were known to fly up to Army helicopters in the air and pace them and just observe. They also observed ground activities. Helicopter door gunners were told not to fire on the UFOs because no one really knew what they were or their capabilities. I have observed them and was told never to tell what I saw and was informed I could be imprisoned and etc. if a riot or whatever broke out as a result. I have no doubt aliens are here now and for the most part look like us."
Also check out The Nha Trang UFO Incident which took place in 1966 causing electromagnetic effects on the ground below.