The show's eighteenth season -- which will air early next year and be the first edition broadcast in HDTV -- will be an all-stars edition comprised of former contestants, according to eyewitness sightings of the racing teams.
Production on the show is believed to have begun on Saturday when airport patrons spotted numerous former The Amazing Race teams boarding flights for Sydney, Australia at Los Angeles international Airport in Los Angeles, CA.
Limiting the edition's cast to The Amazing Race's last six seasons is consistent with the fact that The Amazing Race: All-Stars, the show's prior 2007 all-stars edition, was the reality franchise's eleventh season. However it is not immediately clear why the cast does not seem to include a thirteenth-season team or features so many Season 14 racers.
CBS announced The Amazing Race will begin filming in high definition and air in HDTV earlier this month.
"We're thrilled the audience watching us sprint around the globe each week will continue to witness the breathtaking landscapes that serve as our backdrops, only now in high definition," The Amazing Race executive producer and co-creator Bertram van Munster said.