IMHO, unexplained aerial phenomena (I hate the term 'UFOs') are quite an open question.
There is a lot of data out there to establish the reality of the phenomenon and that a significant number of events are unexplained.
Probably the best are a number of radar/visual cases occurring in the 1950s and 1960s, in which multiple radars and multiple aircraft all tracked an anomaly for a lengthy period of time.
For a good summary of unexplained cases, I recommend looking up the report of the Sturrock Panel (http://www.ufoevidence.org/topics/SturrockPanel.htm). This panel examined some of the best evidential aerial anomaly cases and concluded that there was a significant unexplained component to the UFO phenomenon. There are several other good reports, but I recommend this one as a good place to start.
Slashdot Mirror
IMHO, unexplained aerial phenomena (I hate the term 'UFOs') are quite an open question. There is a lot of data out there to establish the reality of the phenomenon and that a significant number of events are unexplained. Probably the best are a number of radar/visual cases occurring in the 1950s and 1960s, in which multiple radars and multiple aircraft all tracked an anomaly for a lengthy period of time. For a good summary of unexplained cases, I recommend looking up the report of the Sturrock Panel (http://www.ufoevidence.org/topics/SturrockPanel.htm). This panel examined some of the best evidential aerial anomaly cases and concluded that there was a significant unexplained component to the UFO phenomenon. There are several other good reports, but I recommend this one as a good place to start.