Belgium experienced a wave of UFO sightings somewhere between November 1989 and October 1993.
This so called Belgian Flap is probably one of the most well documented UFO cases of all time. It's also very special, since the Govt was very forthcoming in investigating the whole thing and the process was completely transparent!
The crafts sighted were the triangular type UFOs aka ARV, TR-3B, Dudley Dorito which in recent times can be very well attributed to some next generation USAF technology. Whatever the truth may be, this is one case will linger in memory for a long long time.