This term usually refers to those that are wealthy enough to travel and jet around the world. It was a more common phrase around the 1960's and the 1970's. They would go to events other people could not go to because of their location, and they would just 'jet' there.
The correct spelling is "jet skis." It is a plural term referring to the personal watercraft designed for one or two riders. The term "jet ski" is actually a trademarked name originally associated with a specific brand of watercraft, but it is commonly used to refer to similar types of vehicles.
Jet set is a term describing the lifestyle of affluent members of society who travel all around the world, often by way of private jets. The coining of this term can be attributed to Igor Cassini, a reporter for the New York Journal-American who wrote under the pseudonym of "Cholly Knickerbocker".
Jet Set Willy happened in 1984.
Jet Set Willy was created in 1984.
Jet Set Satellite was created in 1998.
Jet Set Radio happened in 2000.
Mungolian Jet Set was created in 2005.
Songs for the Jet Set was created in 2002.
Jet Set Men was created in 1999.
Jet Set Racing was created in 2005.
Jet Set Racing happened in 2005.
American Jet Set was created in 1999.