Did President John F. Kennedy see a UFO?

This article says he did.

Just a few minutes into the cruise everyone on board the launch (including JFK) were stunned when a disc-shaped object appeared within several hundred feet of their boat. The object was about 60 feet in diameter. The middle was slightly raised and part of a top that was a dull, metallic grayish color. The bottom of the craft was very shiny and hard to look at. There were no noticeable windows or openings. The object seemed noiseless and no signs of obvious propulsion could be seen.

It has also been reported that Kennedy met with UFO contactee George Adamski.

This leads to Adamski's claim that he secretly met with President Kennedy around October 1961 to deliver a message from the “space brothers.” According to Major Pederson, the message contained advise on a world crisis to occur in about a year that was later revealed to be the October 1962 Cuban Missile crisis. If true, the contents of the message may have helped Kennedy develop the right strategy for dealing with a conflict that could easily have escalated into a Third World War. The extraterrestrial message, apparently, also contained an invitation for Kennedy to meet with them in Calfornia.