This isn't about conspiracy theories as such, but about 2 incidents that have been widely reported and investigated that have caught my imagination.

The first one is the Begian UFO sightings in the late 80's / early 90's where large triangular shaped craft were seen all over Belgium by quite a few normal people and members of the Police. The Belgian Airforce took an interest and at one point scrambled jets to intercept, locked on to the craft on radar but could not catch it.

http://www.youtube.com/watch?v=RLjd88-PGgM

The second is the UFO sightings in 1976 over Tehran in Iran, again the airforce in that country scrambled jets to intercept, got lock on by radar as well as having visual confirmation but had their instruments inside the plane die on them, only for them to return to normal when they disengaged the object.

http://en.wikipedia.org/wiki/1976_Tehran_UFO_incident

I'm usually quite sceptical about things like this, but the fact so many professional people witnessed these events make me wonder. Whats your thoughts?