There are roughly 600-700 reported sightings annually.
An alien report sighting can be reported to the local media or to NASA. Often times sightings can be found to be a fraud and will be put aside for more important tasks.
There have been so many sightings of UFOs that it is nearly impossible to calculate the exact number of UFO sightings, but there has been an increase in the sightings ever since the late nineties to early eighties. At that time technology and communication form was advancing, and the very popular and intriguing TV show called THE X-files aired.
The best one is the National UFO Reporting Center.
Center for Investigative Reporting was created in 1977.
Pulitzer Center on Crisis Reporting was created in 2006.
National Visitor Center was created in 1976.
Autry National Center was created in 2003.
The National Conference Center was created in 1974.
Center for National Response was created in 1954.
National Center for Simulation was created in 1993.
National Eagle Center was created in 1989.
National Ice Center was created in 1995.