The Collaborative International Dictionary of English v.0.48:

jet set \jet" set`\ n. [from jet plane, the conveyance used in
   their travels.]
   an international group of wealthy individuals who travel
   frequently to international resorts. -- the group is not
   organized, but membership is defined solely by frequent
   travel for pleasure.
   [PJC]

WordNet (r) 3.0 (2006):

jet set
    n 1: a set of rich and fashionable people who travel widely for
         pleasure

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "jet set":
   Vanity Fair, adventurer, alpinist, astronaut, beau monde,
   beautiful people, best people, cafe society, camper,
   carriage trade, climber, comers and goers, commuter, cosmopolite,
   cream of society, cruiser, drawing room, elite, excursionist,
   explorer, fare, fashionable society, globe-girdler, globe-trotter,
   goer, good society, hajji, haut monde, high life, high society,
   in-crowd, jet-setter, jeunesse doree, journeyer, mariner, monde,
   mountaineer, palmer, passenger, passerby, pathfinder,
   people of fashion, pilgrim, pioneer, polite society, right people,
   rubberneck, rubbernecker, sailor, salon, sightseer, smart set,
   social register, societe, society, straphanger, the Four Hundred,
   ton, tourer, tourist, trailblazer, trailbreaker, transient,
   traveler, trekker, tripper, upper crust, uppercut, viator,
   visiting fireman, voortrekker, voyager, voyageur, wayfarer,
   world of fashion, world-traveler